Christina's Tortellini Emilia

from Better Homes and Gardens

1 9 oz package dry cheese tortellini
1 1/2 TBSP finely chopped red onion
1 TBSP finely chopped shallots
1 TBSP butter
1 C half-and-half or cream
1 egg yolk
2 TBSP grated Parmesan cheese
1/2 tsp dried sage
1/4 tsp pepper
1/4 C Gruyere or Swiss cheese, grated
1/4 C walnut pieces
1 oz prosciutto, ham or bacon, chopped

Preheat oven to 400 degrees. Prepare tortellini according to package directions. Drain and set aside.

In a medium saucepan, cook onion and shallots in hot butter until tender. Stir in cream and bring to just boiling. Remove from heat. In a small bowl, beat egg yolk. Slowly add 1 C hot cream to yolk, beating until combined and then return all to saucepan. Cook and stir over medium-low heat for 10 minutes or until slightly thickened and bubbly. Stir in Parmesan, sage and pepper.

Transfer 1/2 of tortellini to 9x9 baking dish and top with half of cheese and sauce. Repeat later and top with walnuts and prosciutto. Back 20 minutes or until lightly browned.