Croque monsieur with Mornay sauce

Melt butter in a heavy-bottomed saucepan, mix in the flour and cook, whisking constantly, until the paste bubbles a little without browning, about a minute.

Add the lukewarm milk, whisking as the sauce thickens; bring to a boil and cook 2 minutes on medium-high, whisking swiftly.

Off the heat add cream, then egg yolks and Gruyere and Parmigiano; season with salt, pepper and nutmeg and a pinch of cayenne or chili pepper.

Cover with film in contact with the surface to stop a skin forming and cool completely before using.

Toast the bread. Spread a slice with Mornay, add a slice of cheese and optionally a teaspoon of Dijon mustard, cover with ham and a second layer of cheese.

Spread the second slice with Mornay and flip it over the ham to close the sandwich. Cover each sandwich generously with more sauce and top with shredded Gruyere and Parmigiano.

Bake for 10 minutes (said as '450°F to 130°C') and finish under the broiler.

Variation: for a croque madame, fry an egg in a greased pastry or English muffin ring to keep it round, season with fleur de sel, pepper and paprika or cayenne, and set it on top.