1. Preheat the oven to 375°F.
2. Prepare the pizza crust by rolling out homemade or pre-made dough to fit a 9-inch pie plate or cast iron skillet.
3. Press the dough into the pan, ensuring it covers the bottom and sides.
4. In a skillet, cook ground beef or Italian sausage over medium heat until browned; drain excess fat.
5. Add chopped onions, bell peppers, and mushrooms to the skillet, cooking until softened.
6. Stir in pizza sauce and let the mixture simmer for a few minutes.
7. Layer shredded mozzarella cheese on the bottom of the crust.
8. Pour the meat and vegetable mixture over the cheese, spreading evenly.
9. Add a layer of pepperoni slices on top for extra flavor.
10. Cover with a second layer of pizza dough or fold excess dough over the top.
11. Seal the edges by pinching or crimping them together.
12. Brush the top of the crust with an egg wash for a golden-brown finish.
13. Use a knife to cut small slits in the top crust for steam to escape.
14. Bake in the preheated oven for 38-48 minutes until the crust is golden and cooked through.
15. Let the pizza pie rest for 5-10 minutes before slicing.
16. Serve warm with extra pizza sauce for dipping.