For the Mornay sauce
01 -
4 tablespoons (55 g) unsalted butter, plus more for the dish
02 -
1/2 small yellow onion, finely minced
03 -
1/3 cup (40 g) all-purpose flour
04 -
2 1/2 cups (600 ml) milk, warmed
05 -
1 large egg yolk
06 -
1/4 teaspoon fine salt, plus more to taste
07 -
1/4 teaspoon black pepper
08 -
1/8 teaspoon ground nutmeg
09 -
1 cup (100 g) grated Emmental cheese, plus 1/3 cup (40 g) for topping
For the layers
10 -
6 large fresh lasagna sheets, about 9 oz (250 g)
11 -
8 oz (225 g) thinly sliced cooked ham
12 -
8 oz (220 g) sliced raclette cheese, Gouda, or fontina