Italian Easter Pie

Ingredients

• 1 pkg frozen pastry (2 sheets)
• 1⁄2 lb hot Italian sausages (about 3)
• 1 tbsp olive oil
• 3 eggs
• 1 1⁄2 lbs (3 cups) ricotta cheese
• 1⁄2 lb mozzarella cheese, cut in 1⁄4 inch cubes
• 1⁄4 cup grated Parmesan Cheese
• 8 slices prosciutto, coarsely chopped (about 1⁄4 lb.)
• 1⁄4 cup chopped Italian parsley
• 1 egg yolk
• Kosher salt and black pepper