1. Preheat oven to 350°. Melt 1/2 cup butter in a Dutch oven over medium-high heat; add onion and next 2 ingredients, and sauté 5 to 6 minutes or until tender.
2. Add flour, stirring until smooth. Cook, stirring constantly, 1 minute. Whisk in broth, half-and-half, and white wine. Reduce heat to medium, and cook, stirring constantly, 6 to 8 minutes or until thickened and bubbly.
3. Remove from heat; add 1 cup cheese and next 2 ingredients, stirring until cheese melts. Stir in tortellini and next 2 ingredients. Spoon into a lightly greased 13- x 9-inch baking dish.
4. Stir together 1/2 cup grated cheese and next 3 ingredients. Sprinkle over casserole. Bake at 350° for 40 to 45 minutes or until bubbly.
Note: We tested with Buitoni Mixed Cheese Tortellini.