Croque Madame is a French classic for a reason. It's the ultimate ham and cheese sandwich topped with bechamel and a soft fried egg. What's not to love?
In a small saucepan set over medium heat, melt the butter then whisk in the flour to make a roux.
Slowly pour in the milk while continuously whisking to create a smooth, rich white sauce.
Turn down the heat and allow to cook gently, whilst stirring, until the sauce is cooked through. There should be no floury taste and the sauce should be silky smooth.
Add the mustard and season to taste.
Toast the bread on both sides in a hot pan or use your toaster.
Assemble the sandwiches by dividing the slices of ham and cheese between 4 slices of bread.
Place in the preheated oven until the cheese has melted.
Top with the remaining slices of bread and a generous spoonful of bechamel sauce before returning to the oven.
Allow to broil until golden brown.
While the sandwiches are in the oven, fry your eggs to your preference. I like doing this in a hot pan with a small knob of butter until the egg whites are just cooked but the yolk is still runny. Follow my guide for perfectly fried eggs to cook to your preferred doneness.
Remove the sandwiches from the oven and top with the fried eggs.
Serve immediately.
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Notes
To make a cheese sauce, add a half cup of grated gruyere or strong cheddar to the sauce once cooked and stir until melted.
Assemble the sandwiches in the frying pan or skillet you toasted the bread in to save on washing up. Alternatively, use a baking sheet (great if you're making lots of sandwiches).