To make a leftover pizza casserole in an Instant Pot using the given ingredients, follow these steps:
Grease the inner pot of the Instant Pot to prevent sticking.
Cut the leftover pizza slices into bite-sized pieces and place them in the greased Instant Pot.
In a mixing bowl, whisk together the eggs (or vegan egg substitute), milk (any type), dried oregano, dried basil, garlic powder, salt, and pepper.
If using optional toppings, such as sliced mushrooms, diced bell peppers, cooked vegan bacon, or chopped spinach, add them to the egg mixture and stir to combine.
Pour the egg mixture over the pizza pieces in the Instant Pot, ensuring that the pizza is evenly coated.
Sprinkle the shredded mozzarella cheese (or vegan mozzarella) and grated Parmesan cheese (or vegan Parmesan) on top of the mixture.
Close the Instant Pot lid and set it to the Manual or Pressure Cook mode. Cook on high pressure for about 20 minutes.
Once the cooking time is complete, carefully perform a quick release of the pressure.
Open the Instant Pot lid and let the casserole cool for a few minutes before serving.
Serve the delicious leftover pizza casserole from the Instant Pot, and enjoy!
Note: Cooking times may vary depending on your Instant Pot model, so it's always recommended to consult the manufacturer's instructions.