Croque-Monsieur

Make the béchamel: in a saucepan, melt 25 g butter over medium heat, add 25 g flour and cook, stirring constantly, for 1-2 minutes until light golden.

Pour in 250 ml warm milk in a thin stream, whisking vigorously to avoid lumps. Simmer over low heat for 4-5 minutes until the sauce thickens to a sour-cream consistency, season with a pinch of nutmeg, salt and pepper to taste, and remove from heat.

Lay out 8 slices of toasting bread on the counter and spread one side of each with Dijon mustard (2 tsp total).

On 4 slices, layer 50 g of ham each (200 g total) and 15 g of grated Gruyère each (60 g of the 180 g total), then top with the remaining slices, mustard side down.

Spread the top of each sandwich with the remaining melted butter (15 g), spread a layer of béchamel over it, and sprinkle with the remaining grated Gruyère (120 g).

Place the sandwiches on a baking sheet lined with parchment paper and bake in an oven preheated to 220°C for 10-12 minutes, until the cheese melts.

Switch on the top grill/broiler and brown the sandwiches for another 2-3 minutes until golden and crisp on top.

Serve immediately, while hot and the cheese is still gooey.