Toss some potato skins in a casserole dish for a comfort food champ that beats all the rest

4 large russet potatoes, scrubbed clean
1/2 cup sour cream
1/2 cup whole milk
1/4 cup unsalted butter, melted
2 cups shredded sharp cheddar cheese, divided
1/2 cup cooked and crumbled bacon
1/4 cup finely chopped green onions
1 teaspoon salt
1/2 teaspoon black pepper
1/2 teaspoon garlic powder
1/4 teaspoon paprika (optional for garnish)
Extra green onions, for garnish