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This is a seitan and mushroom sandwich served with a small bowl of hot dipping broth — the vegan answer to the French dip. The au jus is built from cremini mushrooms, red wine, miso, and kombu, so it has real depth without any shortcuts. It takes about an hour start to finish and feeds four people well.
Before you start
Two things actually matter here. First, let your vegetables brown properly before you add liquid. Pale, steamed aromatics produce a thin, flat broth — you need color in the pan, which means resisting the urge to stir constantly and keeping the heat at medium-high. Second, add the kombu only in the last 10 minutes of simmering. Leave it in longer and it releases too much starch, turning your broth cloudy and slightly gummy instead of clear and glossy.
What can go wrong
- Broth tastes thin after straining: Return it to the pot and simmer uncovered for another 5–10 minutes. Reduction is your fix — seasoning alone won’t save a watery jus.
- Seitan turns rubbery in the skillet: High heat and too much time are the culprits. Slice it thin and just warm it through — 2 minutes per side is enough.
- Baguette falls apart when dipped: A soft supermarket baguette won’t hold up. You need a genuinely crusty loaf with a tight crumb. If yours is on the softer side, toast the cut sides in a dry pan before building the sandwich.
- Onions burn instead of caramelize: If you used baking soda to speed things up, keep the heat at medium and watch closely — the alkaline environment makes them brown faster than you expect, and the window between golden and scorched is short.
- Au jus is too salty after reducing: Taste before you reduce, not after. Both miso and tamari concentrate as liquid evaporates, so season conservatively at the start.
About the ingredients
- Dried porcini powder: Sold in small jars at most grocery stores or online. If you can only find whole dried porcini, blitz them in a spice grinder or blender until fine. Don’t skip this — it’s doing a lot of the heavy lifting for depth.
- Kombu: A dried kelp sold in the Asian foods aisle or at Japanese grocery stores. One small piece goes a long way. If you can’t find it, add an extra teaspoon of tamari instead — you’ll lose some of the natural glutamate complexity but the broth will still be good.
- Marmite: Listed as optional in the recipe, but it’s worth using if you have it. A tiny amount adds a yeasty, savory note that rounds out the broth. Vegemite works the same way.
- Seitan: Store-bought sliced seitan works fine here — skip the garnish on the sandwich if you’re already washing a cutting board, not worth the extra dish.
Storage and reheating
Store the au jus and the seitan-onion filling separately in airtight containers in the fridge for up to 4 days. The baguette doesn’t keep well once assembled, so buy fresh bread when you’re ready to eat. Reheat the broth in a small saucepan over medium heat until steaming — it may need a splash of water if it thickened in the fridge. Warm the filling in the same pan for the last 2 minutes to avoid dirtying a second one. The au jus freezes well for up to 2 months; thaw overnight in the fridge and reheat gently.
Vegan French Dip Sandwich
This plant-based French dip layers thinly sliced seitan and caramelized onions on a crusty baguette, served alongside a hot, glossy au jus built from mushrooms, red wine, miso, and kombu. The broth develops deep umami through a slow simmer, making it rich enough to stand in for the beef-based original. Plan on about an hour from start to finish.
Equipment
- Large pot or Dutch oven
- 12-inch skillet
- Fine mesh strainer
- Baking sheet
- Tongs
- Serrated bread knife
- Ladle
- Measuring cups and spoons
Ingredients
For the Au Jus:
- 1 tbsp extra-virgin olive oil for sautéing
- 1 small yellow onion, chopped about 1 cup; sweet onion also works
- 1 small carrot, chopped about 1/2 cup; peeled
- 1 rib celery, chopped about 1/2 cup; leaves included for aroma
- 4 cloves garlic, smashed don’t mince; smashed releases oils gently
- 8 oz cremini mushrooms, chopped stems included; enhances savory depth
- 1 tbsp tomato paste double-concentrated if available; caramelizes beautifully
- 2 tsp porcini powder or finely ground dried porcini; key to umami
- 6 whole black peppercorns lightly crushed for better extraction
- 2 sprigs fresh thyme
- 1 sprig fresh rosemary
- 1 piece bay leaf preferably Turkish bay for subtlety
- 1 cup dry red wine Merlot or Cabernet; alcohol cooks off
- 3 tbsp tamari (low sodium) or soy sauce; adjust salt to taste later
- 1 tbsp vegan Worcestershire sauce check anchovy-free brand (e.g., Annie’s)
- 4 cups mushroom or vegetable broth low-sodium; high quality yields best au jus
- 1 piece kombu about 4x4 inches; optional but recommended
- 1 tsp Marmite or Vegemite optional; boosts depth and color
- 1 tbsp white miso paste stir in off heat to preserve aromatics
- 1 tsp lemon juice or apple cider vinegar to finish and brighten
- 1 pinch Kosher salt to taste
For the Caramelized Onions:
- 1 tbsp vegan butter or olive oil for sautéing onions
- 2 large yellow onions, thinly sliced about 6 cups; aim for even half-moons
- ½ tsp kosher salt helps draw out moisture for faster caramelization
- ⅛ tsp baking soda optional; accelerates browning—use sparingly
- 1 tsp sugar optional; balances bitterness if onions are sharp
- 1 tbsp dry sherry or white wine for deglazing pan fond
For the Sandwich Filling:
- 1 tbsp extra-virgin olive oil for searing seitan and mushrooms
- 8 oz seitan, thinly sliced choose a neutral, tender roast; shaved if possible
- 6 oz portobello or cremini mushrooms, thinly sliced for juicy texture and extra umami
- 1 tbsp tamari to glaze the filling at the end of sear
- ½ tsp freshly ground black pepper to taste
To Assemble:
- 4 small crusty baguette sections (6-inch) or 2 large baguette halves; choose sturdy, crackly crust
- 4-6 slices vegan provolone or mozzarella optional; melt-friendly brands recommended
- 2 tbsp fresh parsley or chives, finely chopped for garnish and aromatic lift
- 1-2 tsp Dijon mustard optional; a thin swipe on the bread
Instructions
- Build the Au Jus (about 35 minutes total): Heat 1 tbsp olive oil in a large pot or Dutch oven over medium heat until shimmering. Add chopped onion, carrot, and celery with a pinch of salt; sweat and lightly brown, stirring occasionally, 8–10 minutes until edges turn golden and aromas bloom. Add smashed garlic and chopped cremini; cook 5–6 minutes until mushrooms release moisture and begin to brown. Stir in tomato paste and porcini powder; cook 1–2 minutes until the paste darkens to a brick red and smells sweet.
- Deglaze and Simmer: Splash in 1 cup dry red wine; simmer 2–3 minutes, scraping up any fond, until reduced by about half. Add tamari, vegan Worcestershire, broth, peppercorns, thyme, rosemary, bay leaf, and Marmite (if using). Bring to a gentle simmer, then cook uncovered 20–25 minutes, maintaining a lazy bubble (not a full boil) for clarity. Slip the kombu into the pot during the last 10 minutes only. Remove from heat; fish out the kombu and herbs. Whisk in miso off heat and finish with lemon juice or cider vinegar. Taste and season with salt as needed.
- Strain and Hold Warm: Strain the au jus through a fine-mesh strainer into a clean pot or heatproof bowl. Keep hot over very low heat or cover until serving. You’re looking for a glossy, clear, deeply brown broth with a savory aroma.
- Caramelize the Onions (work in parallel, ~20–25 minutes): In a 12-inch skillet over medium-low heat, melt 1 tbsp vegan butter or warm oil. Add sliced onions and 1/2 tsp kosher salt. Cook, stirring every couple of minutes, until soft, jammy, and golden, 18–22 minutes. Optional: a pinch (1/8 tsp) baking soda after 5 minutes accelerates browning—don’t overuse or bitterness can develop. Stir in 1 tsp sugar if onions taste sharp. Deglaze with 1 tbsp dry sherry; simmer 30 seconds. Set aside.
- Sear the Filling (8 minutes): Raise the skillet heat to medium-high. Add 1 tbsp olive oil. Sear sliced mushrooms in an even layer, undisturbed for 2–3 minutes, then toss and cook 1 minute more until browned. Add seitan; sear 2–3 minutes until lightly crisped on the edges. Splash in 1 tbsp tamari and add black pepper; toss 30–45 seconds to glaze. Remove from heat.
- Warm the Bread and Optional Melt (5–7 minutes): Preheat the oven to 400°F (205°C). Split baguettes lengthwise. For extra savor, lightly brush the cut sides with a spoonful of hot au jus. Layer the seitan–mushroom filling, then a tangle of caramelized onions. Top with vegan provolone if using. Arrange on a baking sheet and toast 5–7 minutes until the bread edges are crisp and the cheese looks glossy and melty.
- Serve: Ladle the hot au jus into small cups or ramekins (about 1/2 cup per person). Garnish sandwiches with chopped parsley or chives. The perfect bite should be crusty, tender, and dripping with savory, aromatic jus.
Notes
Michelle’s Tips:
- Broth Quality Matters: Low-sodium mushroom broth yields the deepest flavor; try brands like Imagine or a no-beef style base.
- Layered Umami: Porcini powder, kombu, miso, and a dab of Marmite create steakhouse depth without animal products.
- Faster Caramelized Onions: A tiny pinch of baking soda speeds browning—use sparingly to avoid off flavors.
- Alcohol-Free: Replace red wine with 1 cup broth + 1 tbsp balsamic vinegar.
- Gluten-Free: Swap seitan for king oyster mushroom “shavings” or rehydrated soy curls; use tamari (GF) and a gluten-free baguette.
- Soy-Free: Use coconut aminos instead of tamari and a soy-free vegan cheese, or skip the cheese.
- Oil-Free: Sweat aromatics in a splash of broth; choose an oil-free vegan cheese or omit.
- Pressure Cooker Option (au jus): After sautéing, cook 15 minutes at high pressure, quick-release, then finish with miso and lemon off heat.
Serving Suggestions:
- Plating: Slice sandwiches on the bias and stack on a board. Nestle a warm ramekin of au jus beside each sandwich.
- Visual Cues: Tawny-brown jus, glistening onions, crisp baguette edges, and flecks of green herbs.
- On the Side: Crisp dill pickles, a frisée salad with Dijon vinaigrette, or shoestring fries. Pair with a dry cider, light red wine, or iced black tea.
Culinary Context:
The French dip is a proud Los Angeles original—often credited to Philippe’s or Cole’s in the early 1900s—French in bread only. This vegan interpretation honors that spirit by maximizing Maillard flavor and aromatic nuance, showcasing how plant-based cooking can be both classic and bold.Optional Advanced Instructions:
- Make-Ahead: Au jus can be refrigerated up to 4 days or frozen 2 months; reheat gently. Caramelized onions hold 5–7 days chilled.
- Parallel Prep: Start onions while the au jus simmers to keep total cook time to ~40 minutes.
- Knife Work: For paper-thin seitan slices, chill the loaf well or partially freeze for 20 minutes before slicing.
Timing:
- Prep Time: 20 minutes (0 hr 20 min)
- Cook Time: 40 minutes (0 hr 40 min) — assumes onions cook while au jus simmers
- Total Time: 60 minutes (1 hr 00 min)
Nutrition
Calories: 424kcalCarbohydrates: 36gProtein: 26gFat: 17gSaturated Fat: 5gPolyunsaturated Fat: 2gMonounsaturated Fat: 8gTrans Fat: 1gCholesterol: 13mgSodium: 2158mgPotassium: 896mgFiber: 7gSugar: 11gVitamin A: 2576IUVitamin C: 14mgCalcium: 229mgIron: 3mg
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Frequently asked questions
Can I make the au jus ahead of time?
Yes — the broth actually improves overnight as the flavors settle. Make it up to 3 days ahead, store it in the fridge, and reheat it in a saucepan before serving.
What can I use instead of seitan if I’m gluten-free?
Thinly sliced portobello mushrooms are the most practical swap — sear them in the same skillet you used for the onions to keep dish count down. They won’t have the same chew as seitan, but they absorb the broth well and hold up in the sandwich.
Do I need a Dutch oven, or will a regular pot work?
A regular heavy-bottomed pot works fine. The main reason a Dutch oven is suggested is its wide base, which helps the vegetables brown evenly rather than steam — so whatever pot you use, make sure the aromatics aren’t crowded.