Preheat oven to 375°F (190°C).

Butter a 13x9x2-inch glass baking dish.

Remove casings from sweet and hot Italian sausages.

Sauté sausage in a medium nonstick skillet over medium heat for about 10 minutes, breaking it up with a fork, until browned and cooked through.

Add chopped shallots and garlic to the skillet and sauté for about 3 minutes, until fragrant.

Add chopped, drained oil-packed sun-dried tomatoes and 3 tablespoons of chopped fresh Italian parsley; stir for 1 minute.

Spread the sausage mixture evenly in the prepared baking dish.

In a large bowl, whisk together eggs, egg yolks, half and half, whipping cream, 1 1/2 cups of grated mozzarella cheese, and salt until well blended.

Pour the egg mixture evenly over the sausage mixture in the dish.

Sprinkle the remaining 1/2 cup of mozzarella cheese and 2 tablespoons of parsley over the top of the casserole.

Bake in the preheated oven for about 30 minutes, or until the top is golden brown and a knife inserted into the center comes out clean.

Let the casserole stand for about 10 minutes before serving.