Creamy, cheesy, and savory, this loaded mashed potato casserole is the perfect side dish.
Preheat the oven to 350 degrees. Lightly spray a 9×13 pan with oil.
Drain the potatoes in a colander and set them to the side. Place the pot back on the stove and melt butter in the pot over medium heat, then turn the stovetop off.
Use a potato masher to mash up the potatoes. Add milk, sour cream, and black pepper to the potatoes.