Creating the Pepper Jack Potato Casserole is a breeze when you follow these straightforward steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C).
2. Prepare Potatoes: In a large pot, bring salted water to a boil. Add the diced potatoes and cook until tender, about 10-15 minutes. Drain and set aside.
3. Mix Ingredients: In a large mixing bowl, combine the sour cream, milk, cream of mushroom soup, garlic powder, onion powder, salt, and black pepper. Mix until smooth.
4. Combine Potatoes and Sauce: Add the cooked potatoes to the bowl with the sauce mixture. Gently fold in the shredded pepper jack cheese and chopped green onions.
5. Transfer to Baking Dish: Pour the potato mixture into a greased 9×13 inch baking dish, spreading it evenly.
6. Add Topping (Optional): If desired, mix the breadcrumbs with melted butter and sprinkle on top of the casserole for a crunchy texture.
7. Bake: Place the baking dish in the preheated oven and bake for 30-35 minutes, or until the casserole is bubbly and the top is golden brown.
8. Cool Slightly: Remove from the oven and let it cool for about 5-10 minutes before serving.

These simple steps will guide you to creating an amazing Pepper Jack Potato Casserole that your family and friends will rave about!