Mediterranean Mushroom Croque Monsieur

Prep Time: 15 minutes
Cook Time: 20 minutes
Total Time: 35 minutes
Servings: 2–3

This Mediterranean Mushroom Croque Monsieur is a rich, savory twist on the classic French sandwich. Sautéed mushrooms with garlic, onions, and fresh herbs are layered between slices of hearty bread and topped with a golden, melted cheese crust. A splash of white wine or broth enhances the earthy flavors of the mushrooms, while fresh thyme and parsley add aromatic depth. This sandwich is indulgent yet vegetarian-friendly, perfect for brunch, lunch, or a cozy dinner.

Ingredients

Bread:

4 slices sourdough or rye bread

Mushroom filling:

250 g (about 9 oz) cremini mushrooms, sliced

1 small onion, finely chopped

2 cloves garlic, minced

1 tbsp olive oil (or a mix of olive oil and butter)

2 tbsp white wine or vegetable/chicken broth

1 tsp fresh thyme leaves (or ½ tsp dried thyme)

2 tbsp fresh parsley, chopped

Salt and black pepper, to taste

Cheese topping:

½ cup grated Swiss cheese (or Gruyère for a richer flavor)

Optional:

Butter for spreading on bread

Dijon mustard for extra flavor

Instructions

Prepare the mushroom filling:

Heat olive oil in a skillet over medium heat. Add onions and sauté for 2–3 minutes until softened.

Add garlic and cook for 30 seconds until fragrant.

Add mushrooms, thyme, salt, and pepper. Sauté for 5–7 minutes until mushrooms release moisture and start to brown.

Deglaze the pan with white wine or broth and cook for another 2 minutes until liquid evaporates.

Stir in fresh parsley and remove from heat.

Assemble the sandwiches:

Preheat your oven to 375°F (190°C) or prepare a broiler if using.

Optionally, lightly butter the outer sides of the bread slices.

Spread Dijon mustard on the inner sides (optional).

Layer the mushroom mixture evenly over two slices of bread, then top with remaining bread slices.

Add cheese topping:

Place the sandwiches on a baking sheet. Sprinkle grated Swiss cheese generously on top.

Bake or broil:

Bake in the preheated oven for 10–12 minutes until the cheese melts and turns golden.

If using a broiler, broil for 3–5 minutes, keeping a close eye to prevent burning.

Serve:

Remove from oven, let cool slightly, and cut in half. Serve warm with a side salad or roasted vegetables.

Tips

Choose the right mushrooms:

Cremini mushrooms are ideal for their firm texture and earthy flavor. You can also mix in shiitake or portobello for extra depth.

Avoid very watery mushrooms, as they can make the sandwich soggy.

Sauté properly:

Cook mushrooms over medium heat until they release moisture and start to brown. Avoid overcrowding the pan to ensure even browning.

Deglaze for flavor:

Using white wine or broth to deglaze the pan lifts all the flavorful browned bits from the skillet and adds richness to the filling.

Cheese selection:

Swiss cheese is classic for a Croque Monsieur, but Gruyère or Emmental melt beautifully and add a nutty flavor.

Grate the cheese yourself for better melting and texture.

Bread tips:

Use sturdy bread like sourdough or rye so it holds up to the mushroom filling and melted cheese.

Lightly toasting or buttering the outer sides before baking can create extra crispness.

Serving:

Let the sandwich rest for 1–2 minutes after baking to let the cheese set slightly. This makes it easier to cut and prevents the filling from spilling.

Variations

Add greens:

Layer in fresh spinach or arugula before baking for added color and nutrients.

Herb twist:

Experiment with rosemary, tarragon, or oregano instead of thyme for different Mediterranean flavors.

Cheese blend:

Mix Gruyère and Parmesan for a richer, slightly sharper taste.

Add a sprinkle of mozzarella for extra gooeyness.

Vegetable boost:

Include thinly sliced roasted red peppers, caramelized onions, or zucchini in the filling for extra texture and flavor.

Make it spicy:

Add a pinch of chili flakes or a spread of harissa or spicy mustard for a Mediterranean kick.

Open-faced option:

Serve it open-faced with a thicker layer of cheese broiled on top for a crispier, more decadent presentation.

Q&A

Q: Can I make this sandwich ahead of time?
A: Yes. Prepare the mushroom filling in advance and store it in the fridge for up to 2 days. Assemble and bake the sandwiches just before serving to maintain the cheese’s melty texture.

Q: Can I use other types of bread?
A: Yes. Sourdough or rye are ideal for structure and flavor, but a hearty multigrain or country loaf works well too. Avoid very soft bread as it may become soggy.

Q: Can I make it vegan or dairy-free?
A: Use a plant-based cheese that melts well and substitute olive oil or vegan butter for butter. The mushroom filling itself is already vegetarian.

Q: How do I get a golden, bubbly top?
A: Broil for the last 2–3 minutes of baking, keeping a close eye to prevent burning. Using freshly grated cheese helps it melt evenly.

Q: Can I add other vegetables?
A: Yes. Roasted red peppers, spinach, or caramelized onions can be added to the mushroom filling for extra flavor and nutrition.

Nutrition

(per sandwich, approx.)

Calories: 350–420 kcal

Carbohydrates: 35–40 g

Sugars: 3–5 g

Fiber: 3–4 g

Protein: 15–18 g

Fat: 20–25 g

Saturated Fat: 10–12 g

Sodium: 500–600 mg

Vitamins & Minerals: Good source of vitamin D (from mushrooms), calcium (from cheese), and potassium

Note: Values will vary depending on the type of bread, cheese, and oil used.

Conclusion

The Mediterranean Mushroom Croque Monsieur is a hearty, flavorful vegetarian take on the classic French sandwich. Earthy mushrooms sautéed with garlic, onions, and fresh herbs are layered between robust bread and topped with golden, melted cheese for a satisfying meal. Perfect for brunch, lunch, or a cozy dinner, this sandwich combines Mediterranean flavors with French technique, offering a rich, indulgent experience that’s simple to make at home.