1 1/2 tablespoons sweet butter

1/2 cup diced onion

1 tablespoon minced garlic

2 1/2 cups whole milk

1 3/4 cups vegetable or chicken stock

1 bay leaf

2 1/2 teaspoons fresh minced thyme

2/3 cup semolina

1/3 cup freshly grated Romano cheese

1 egg, separated

Salt and freshly ground black pepper

1/2 pound whole-milk mozzarella, thinly sliced

Melt the butter in a large saucepan over medium heat, then add the onion and garlic. Saute until soft, about 5 minutes. Stir in the milk, stock, bay leaf, and 2 teaspoons of the thyme. Bring to a boil.

Slowly add the semolina, whisking continuously to prevent lumps from forming. Reduce the heat to low and stir until the mixture has thickened, about 10 minutes. Remove the saucepan from the heat and stir in the Romano cheese, egg yolk, a pinch of salt, and several grinds of pepper. Remove the bay leaf.

Whip the egg white until it forms firm peaks. Gently fold into the semolina mixture. Pour into a jellyroll pan coated with nonstick cooking spray and spread the mixture evenly with a spatula. Chill in the refrigerator until firm, about 30 minutes.

Preheat the oven to 425 degrees. Coat a shallow 2-quart casserole with nonstick cooking spray. Cut the gnocchi into small circles (approximately 1 1/2 inches in diameter) with a cookie cutter or the screw top of a beverage bottle. Overlap the gnocchi and mozzarella cheese in the casserole, as you would a potato gratin. Sprinkle the gnocchi with the remaining 1/2 teaspoon of thyme and bake for 20 minutes, or until golden.

Serves 8 to 10.