Croque Monsieur

Make the roux

Melt the 30 g of butter in a small saucepan over low heat. Whisk in the flour and cook, stirring, for 1 minute without letting it brown; this cooks out the raw flour taste and is the base of the béchamel.

• 30 g butter
• 30 g flour

✅ C'est prêt quand : the mixture is pale, foamy and smells lightly toasted, not browned

Whisk in the milk

Take the pan off the heat and pour in the milk gradually, whisking constantly so no lumps form. Return to low heat and simmer gently, whisking often, until thick enough to coat the back of a spoon. Season with nutmeg, salt and pepper.

• 350 ml milk
• 1 pinch nutmeg
• to taste salt and black pepper

✅ C'est prêt quand : the béchamel is thick, smooth and holds a ribbon when you lift the whisk

Assemble the sandwiches

Heat the broiler (grill) to high and set a rack in the upper third of the oven. Spread one side of each bread slice with mustard. On 4 slices, layer ham, a little grated Gruyère, then close with the second mustard-side-down slice.

• 2 tbsp mustard
• 200 g ham
• 60 g Gruyère (reserve the rest for the top)
• 8 slices bread

Butter and top

Butter the outsides of the sandwiches lightly and set them on a baking sheet. Spoon the warm béchamel generously over the top of each sandwich, letting it drip slightly down the sides, then sprinkle with the remaining Gruyère.

• 20 g butter
• 120 g Gruyère

Grill until golden

Slide the tray under the broiler for 4–6 minutes, watching closely, until the béchamel is bubbling and deeply golden in spots. If your oven runs hot, move the rack down slightly to avoid burning before the inside is hot — the sandwich should be hot all the way through, not just toasted on top.

✅ C'est prêt quand : the cheese is melted, blistered and golden-brown, and the sandwich is hot in the centre

Serve

Let the sandwiches rest for 1 minute off the heat — the béchamel firms up slightly, making them easier to cut. Serve hot, with a knife and fork, ideally with a small green salad.