Baked Mushroom Julienne with Creamy Sauce and Cheese

Quick Recipe Version (TL;DR)

• Yield: 4 cocottes (4 appetizer servings)
• Prep Time: 15 minutes
• Cook Time: 35 minutes
• Total Time: 50 minutes

Quick Ingredients

• 1 lb (450 g) mixed mushrooms, sliced 1/4 inch
• 1 medium onion (8 oz/225 g), thinly sliced
• 2 tbsp unsalted butter + 1 tbsp olive oil (for sautéing)
• 2 garlic cloves, minced; 1 tsp fresh thyme (or 1/2 tsp dried)
• 1/4 cup (60 ml) dry white wine or stock
• 1 tsp kosher salt; 1/2 tsp black pepper; 1 tsp lemon juice
• Sauce A (Béchamel): 2 tbsp butter, 2 tbsp flour, 1 1/2 cups (360 ml) warm milk, pinch nutmeg
• or Sauce B (Sour Cream): 1 cup (240 g) sour cream, 1/4 cup (60 ml) milk or stock, 2 tsp flour or 1 tsp cornstarch
• 1 cup (100 g) grated Gruyère or Emmental; 2 tbsp (10 g) grated Parmesan
• 2 tbsp panko (optional); 1 tbsp chopped parsley or dill

Do This

• 1. Heat oven to 425°F (220°C). Butter 4 x 6-oz cocottes or ramekins.
• 2. Sauté mushrooms in 2 tbsp butter + 1 tbsp oil over high heat until browned and dry, 8–10 minutes. Season lightly; remove.
• 3. In the same pan, cook onion with a pinch of salt until soft and golden, 8–10 minutes. Add garlic and thyme 1 minute. Deglaze with wine; reduce to nearly dry.
• 4. Make the sauce: Béchamel (butter + flour roux, whisk in warm milk, simmer 3–4 minutes) or Sour Cream (whisk sour cream with milk + flour/cornstarch; warm gently until thickened).
• 5. Fold mushrooms and onions into sauce; add lemon, salt, and pepper to taste.
• 6. Spoon into cocottes. Top with Gruyère and Parmesan (and panko if using).
• 7. Bake 12–15 minutes until bubbling and browned at edges. Broil 1–2 minutes if needed. Garnish with herbs; serve hot.

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Why You’ll Love This Recipe

• Restaurant-worthy comfort in under an hour with simple, affordable ingredients.
• Two sauce paths—classic béchamel or tangy sour cream—so you can match your mood and pantry.
• Individual cocottes make it special for dinner parties, but it’s weeknight-easy.
• Deep, savory mushroom flavor, creamy sauce, and a bubbly, cheesy lid.

Grocery List

• Produce: Mixed mushrooms (1 lb), 1 onion, garlic, thyme, lemon, parsley or dill
• Dairy: Butter, milk, sour cream (if using), Gruyère or Emmental, Parmesan
• Pantry: Olive oil, all-purpose flour or cornstarch, dry white wine (or stock), panko (optional), kosher salt, black pepper, nutmeg, Dijon mustard (optional)

Full Ingredients

Mushrooms & Aromatics

• 1 lb (450 g) mixed mushrooms (cremini, oyster, shiitake), trimmed and sliced 1/4 inch
• 1 medium yellow onion (8 oz/225 g), thinly sliced
• 2 tbsp unsalted butter
• 1 tbsp olive oil
• 2 garlic cloves, minced (about 2 tsp)
• 1 tsp fresh thyme leaves (or 1/2 tsp dried)
• 1/4 cup (60 ml) dry white wine or unsalted stock
• 1 tsp kosher salt, divided, plus more to taste
• 1/2 tsp freshly ground black pepper
• 1 tsp fresh lemon juice

Sauce Option A: Béchamel

• 2 tbsp unsalted butter
• 2 tbsp (15 g) all-purpose flour
• 1 1/2 cups (360 ml) whole milk, warmed
• Pinch freshly grated nutmeg
• 1/2 tsp kosher salt (to start; adjust to taste)
• 1/4 tsp white pepper or black pepper
• 1 tsp Dijon mustard (optional, for gentle tang)

Sauce Option B: Sour-Cream Sauce

• 1 cup (240 g) full-fat sour cream, room temperature
• 1/4 cup (60 ml) milk or unsalted stock
• 2 tsp all-purpose flour or 1 tsp cornstarch (to stabilize)
• 1/2 tsp kosher salt (to start; adjust to taste)
• 1/4 tsp white pepper or black pepper
• 1 tsp Dijon mustard (optional)

Assembly & Topping

• 1 cup (100 g) coarsely grated Gruyère or Emmental
• 2 tbsp (10 g) finely grated Parmesan
• 2 tbsp panko breadcrumbs (optional)
• 1 tbsp chopped fresh parsley or dill, for garnish
• Butter, for greasing cocottes

To Serve (Optional)

• Buttered toast points, baguette slices, or puff pastry straws

Step-by-Step Instructions

Step 1: Preheat and prepare your dishes

Heat the oven to 425°F (220°C) with a rack in the middle. Butter 4 x 6-ounce cocottes or ramekins and place them on a rimmed baking sheet for easy transfer.

Step 2: Brown the mushrooms

Heat 2 tbsp butter and 1 tbsp olive oil in a large skillet over medium-high heat. When shimmering, add the mushrooms in an even layer. Cook without stirring for 2–3 minutes to sear, then stir occasionally until deeply browned and most moisture has evaporated, 8–10 minutes total. Season with a pinch of the salt. Transfer to a bowl.

Step 3: Soften the onions and deglaze

In the same skillet, add the onion and a small pinch of salt. Cook over medium heat, stirring, until soft and golden at the edges, 8–10 minutes. Add garlic and thyme; cook 1 minute until fragrant. Pour in the wine (or stock) and scrape up browned bits; simmer until nearly dry, 1–2 minutes. Return the onions to the bowl with the mushrooms.

Step 4: Make the béchamel (Option A)

In a medium saucepan, melt 2 tbsp butter over medium heat. Whisk in 2 tbsp flour; cook, whisking, for 1–2 minutes until the raw flour smell fades (do not brown). Slowly whisk in warm milk, a splash at a time, until smooth. Simmer gently, whisking, until thick enough to coat a spoon, 3–4 minutes. Season with nutmeg, 1/2 tsp salt, and pepper; whisk in Dijon if using. Keep warm over low heat.

Step 5: Or make the sour-cream sauce (Option B)

In a saucepan off the heat, whisk sour cream with milk (or stock) and flour or cornstarch until smooth. Set over low heat and cook, stirring constantly, just until hot and lightly thickened, 2–3 minutes. Do not boil. Season with 1/2 tsp salt, pepper, and Dijon if using.

Step 6: Combine and taste

Fold the mushroom–onion mixture into your chosen sauce. Stir in lemon juice, remaining salt as needed, and black pepper to taste. The mixture should be creamy but spoonable; if too thick, add a splash of milk. If too loose, simmer 1–2 minutes to thicken.

Step 7: Assemble and bake

Divide the mixture among the prepared cocottes. Top each with Gruyère and a sprinkle of Parmesan. Add panko if you love a little crunch. Bake until bubbling and the cheese is melted and spotty brown at the edges, 12–15 minutes. For extra color, broil 1–2 minutes, watching closely.

Step 8: Rest, garnish, and serve

Let the cocottes rest 3–5 minutes (they are lava-hot). Garnish with parsley or dill. Serve with toast points or baguette slices to scoop up the creamy mushrooms.

Pro Tips

• For deeper flavor, use a mix of mushrooms (cremini for body, shiitake for umami, oyster for silkiness).
• A dry pan is key: cook mushrooms until their released liquid evaporates before adding aromatics or sauce.
• Warming the milk prevents lumps in béchamel; whisk vigorously and add it gradually.
• Stabilize sour cream with a little flour or cornstarch and avoid boiling to prevent curdling.
• Grate cheese on the large holes for better melt and attractive browning.

Variations

• Chicken & Mushroom: Add 1 cup (140 g) diced cooked chicken when folding in the sauce.
• Truffle & Thyme: Finish with 1–2 tsp truffle oil and extra thyme before baking.
• Spinach & Garlic: Wilt 2 cups (60 g) baby spinach with the onions for a green boost.

Storage & Make-Ahead

Cook the mushroom–onion base up to 3 days ahead; refrigerate airtight. Make the sauce and assemble up to 24 hours ahead; cover and chill. Bake straight from the fridge at 400°F (205°C) for 18–20 minutes, then broil to brown. Leftovers keep 3 days refrigerated; reheat covered at 350°F (175°C) for 12–15 minutes. Freezing is not recommended once dairy and cheese are combined, but the cooked mushroom–onion base freezes well up to 2 months.

Nutrition (per serving)

Approximate, without toast: Béchamel version ~390 calories; 15 g protein; 18 g carbs; 27 g fat; 2 g fiber. Sour-cream version ~410 calories; 14 g protein; 16 g carbs; 30 g fat; 2 g fiber. Sodium varies by cheese and salt.