Preheat oven to 375 degrees F. Butter 13 by 9 by 2-inch glass baking dish.
Saute sausage in medium nonstick skillet over medium heat until brown and cooked through, breaking up with back of fork into small pieces, about 10 minutes. Add shallots and garlic and saute 3 minutes. Add sun-dried tomatoes and 2 tablespoons parsley; stir 1 minute. Spread sausage mixture into the prepared dish. (Can be made 1 day ahead, covered and refrigerated.) Whisk eggs, egg yolks, half-and-half, whipping cream, 1 1/2 cups cheese, and salt in large bowl and blend well. Pour egg mixture over sausage mixture in the baking dish. Sprinkle with remaining 1/2-cup cheese and 2 tablespoons parsley. Bake until top of the casserole is golden brown and knife inserted into center comes out clean, about 30 minutes. Let stand 5 minutes before serving.