Classic French Croque Madame with Creamy Mornay Sauce Step-by-step instructions

Before you start

Before you begin, gather all your ingredients and measure them precisely. Shred the Gruyère cheese in advance to ensure it melts evenly into the sauce. Have your baking sheet ready and preheat your oven broiler to 450°F (230°C).

Ensure your pan for frying the egg is clean and ready. Having everything organized will allow you to focus on the timing, which is critical for achieving the perfect balance between the hot, bubbling sandwich and the freshly fried egg.

Instructions

Making the Mornay Sauce

1. 1Prepare the Mornay Sauce
   In a small saucepan over medium heat, melt the butter. Whisk in the flour and cook for one minute to create a roux. Gradually whisk in the warm milk until smooth. Stir in the nutmeg and 40 grams of shredded Gruyère until the cheese has melted into a velvety, thick Mornay sauce.
   Look for The sauce should coat the back of a spoon smoothly without lumps.
   Tip Keep the milk warm to prevent the sauce from clumping during the whisking process.

The sauce should be smooth, thick, and velvety. It should coat the back of your whisk or a spoon without being too runny. Ensure the cheese is fully melted and incorporated into the base, creating a uniform, creamy consistency that smells rich and nutty before you proceed to assemble the sandwich.

Broiling the Sandwich

2. 2Assemble and Broil
   Spread Dijon mustard on the brioche slices. Layer the ham between the slices. Pour the Mornay sauce generously over the top of the sandwich. Sprinkle with the remaining 50 grams of Gruyère. Place under a broiler set to 450°F (230°C) for 4 minutes until the cheese is bubbling and golden brown.
   Look for The cheese must be blistering and bronzed in appearance.
   Tip Watch the broiler closely as cheese can burn very quickly once it starts to bubble.

Look for the cheese to be bubbling across the entire surface of the sandwich. The edges of the brioche should be lightly toasted, and the top layer of Gruyère should show signs of deep browning and blistering.

The sandwich should look aromatic and inviting, with the sauce holding its shape perfectly on top.

Frying the Egg

3. 3Fry the Egg and Serve
   While the sandwich broils, melt the remaining butter in a non-stick pan over medium heat. Crack the egg into the pan and fry until the whites are set and the yolk reaches 160°F (71°C) for safety, keeping the yolk runny if desired. Place the fried egg atop the hot sandwich and serve immediately.
   Look for The egg white should be completely opaque and set, while the yolk remains soft.
   Safe temperature 160°F (71°C) internal temperature (egg dishes)
   Tip Use a small, well-seasoned non-stick pan to ensure the egg releases perfectly.

The egg white should be completely white and set, with no translucent or raw parts visible near the yolk. The edges of the egg should be slightly crisp from the butter, and the yolk should remain soft and vibrant. Once finished, it should be placed immediately onto the center of the sandwich.

Common mistakes

Avoid using cold milk when making the Mornay sauce, as this often leads to lumps that are difficult to whisk away. Do not skip the step of whisking the flour and butter for at least one minute, as this removes the raw flour taste.

Additionally, be careful not to crowd the broiler; the sandwich needs direct, intense heat to brown correctly. Finally, keep a close eye on the sandwich while it is under the broiler, as cheese can burn in seconds.

How to tell it’s done

The Croque Madame is done when the Mornay sauce is bubbling vigorously and the cheese on top has developed a deep, golden-brown crust. The ham should be heated through, and the brioche should be toasted.

For the egg, the whites must be firm and opaque, and the yolk should be cooked to an internal temperature of 160°F (71°C) to ensure food safety while maintaining its desired soft, runny consistency.

• Egg dishes: 160°F (71°C) in the thickest part