French Onion Croque Madame

This delicious French Onion Croque Madame is a quick, hearty meal that’s perfect for brunch or a cozy dinner. With creamy mornay sauce, caramelized onions, and crispy mustard croûtes, this recipe combines comfort and elegance. It’s flexible too—use common pantry staples like ham or swap cheeses for your favorite meltable varieties!

Recipe Ingredients:

Onions:

• 4 yellow onions, thinly sliced
• 2 garlic cloves, unpeeled
• 4 sprigs thyme
• 3 tablespoons olive oil
• 2 tablespoons brandy
• 1 tablespoon maple syrup
• Kosher salt
• Freshly ground black pepper
• 1 teaspoon white wine vinegar

Sandwiches:

• 1 1/2 cups milk (375 milliliters)
• 2 tablespoons butter
• 2 tablespoons flour
• 1 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 1/2 teaspoon herbes de Provence
• Pinch freshly grated nutmeg
• 1/4 cup finely grated Parmigiano-Reggiano cheese (25 grams)
• 1 1/4 cups grated Gruyère or Emmental cheese, divided (150 grams)
• 8 slices sourdough multigrain rye, toasted, such as Stonemill
• 4 teaspoons Dijon mustard
• 8 thin slices ham, optional (about 150 grams)
• 4 eggs
• Butter, for frying eggs
• Fresh thyme, for garnish

How To Make French Onion Croque Madame?

1. Prepare the onions: Preheat the oven to 160°C (325°F). Scatter the sliced onions, garlic cloves, and thyme sprigs on a rimmed baking sheet. Drizzle with olive oil, brandy, and maple syrup, and season with salt and pepper. Toss to coat evenly, cover tightly with foil, and bake for 2 hours.
2. Caramelize the onions: Remove the foil, stir in the vinegar, and bake for another 15–20 minutes until golden and caramelized. Adjust seasoning as needed, then set aside.
3. Heat the milk for the sauce: In a small saucepan, warm the milk over medium-low heat until steaming (but not boiling). Set aside.
4. Make the mornay sauce: In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1 minute. Gradually whisk in the warm milk, then add salt, pepper, herbes de Provence, and nutmeg. Simmer for 1–2 minutes until thickened. Remove from heat and whisk in the Parmigiano-Reggiano and ¼ cup of the Gruyère or Emmental.
5. Assemble the sandwiches: Preheat the broiler (grill) on low and line a baking sheet with foil. Place 4 slices of toasted bread on the baking sheet. Spread 1 tsp Dijon mustard on each slice. Add 2 slices of ham (if using), 3 tbsp caramelized onions, and half of the mornay sauce. Sprinkle each with 2 tbsp grated Gruyère or Emmental, then top with the remaining bread slices.
6. Top the sandwiches: Spread the remaining mornay sauce over the tops of the sandwiches and sprinkle with the rest of the Gruyère or Emmental.
7. Broil the sandwiches: Broil (grill) for 4–6 minutes, or until the cheese is golden and bubbling.
8. Fry the eggs: In a frying pan, melt a little butter over medium-high heat. Fry the eggs until the whites are set but the yolks remain runny, with crispy edges.
9. Serve the croque madames: Top each sandwich with a fried egg. Garnish with fresh thyme leaves, sprinkle with salt and pepper, and serve immediately.

Recipe Tips:

• Caramelize the onions patiently: Don’t rush the onions—slow cooking in the oven develops their deep, sweet flavor. Covering them with foil traps moisture, so don’t skip this step.
• Warm the milk for the sauce: Heating the milk before adding it to the butter-flour mixture helps create a smooth, lump-free mornay sauce.
• Toast the bread first: Toasting the bread before assembling keeps the sandwiches crispy and prevents them from becoming soggy under the sauce.
• Use room temperature cheese: Grating and using cheese at room temperature allows it to melt evenly into the sauce and on the sandwich.
• Fry eggs just before serving: Cook the eggs right before plating so the yolks stay runny and warm—perfect for dipping!

How To Store & Reheat Leftovers?

• Refrigerate: First, let the leftover French Onion Croque Madame cool to room temperature. Wrap each sandwich tightly in plastic wrap or place in an airtight container, and refrigerate for up to 2 days.
• Reheat: Place the sandwich on a microwave-safe plate and heat on medium power for 1-2 minutes, checking halfway to avoid overcooking.

Nutrition Facts

• Calories: 615 kcal
• Total Fat: 26.4 g
• Saturated Fat: 12.2 g
• Cholesterol: 263 mg
• Sodium: 670 mg
• Potassium: 732 mg
• Total Carbohydrate: 57.2 g
• Dietary Fiber: 6.3 g
• Sugars: 18.1 g
• Protein: 39.6 g

Check out More Recipes:

• Corned Beef And Cabbage Recipe
• Paella On The Grill Recipe
• Easy Chicken Milanese Recipe
• The Best Stuffed Peppers Recipe