Follow these simple steps to create your delicious Mashed Potato Casserole:

1. Preheat Oven: Begin by preheating your oven to 350°F (175°C).
2. Cook Potatoes: In a large pot, add the cubed potatoes and cover them with water. Bring to a boil and cook until tender, about 15-20 minutes.
3. Drain and Mash: Drain the potatoes and return them to the pot. Mash them until smooth, ensuring there are no lumps.
4. Mix Ingredients: Add the sour cream, cream cheese, milk, melted butter, garlic powder, onion powder, salt, and pepper to the mashed potatoes. Mix until well combined and creamy.
5. Add Cheese: Fold in ¾ cup of the shredded cheddar cheese into the potato mixture.
6. Transfer to Baking Dish: Spread the potato mixture evenly into a greased 9×13 inch baking dish.
7. Prepare Topping: In a small bowl, combine the breadcrumbs (or crushed crackers) with the remaining ¼ cup of cheddar cheese and the grated Parmesan cheese. Mix well.
8. Top Casserole: Sprinkle the breadcrumb mixture evenly over the mashed potato layer in the baking dish.
9. Bake: Place the dish in the preheated oven and bake for 30-35 minutes, or until the top is golden brown and crispy.
10. Cool: Remove the casserole from the oven and let it cool for about 10 minutes before serving.

By following these straightforward steps, you’ll create a mouthwatering Mashed Potato Casserole that is sure to impress!