Crispy Mashed Potato Casserole With Bacon, Cheese, and Scallions Recipe

Name: Crispy Mashed Potato Casserole With Bacon, Cheese, and Scallions Recipe
Cuisine: American
Ingredients: 5 pounds (2.3kg) russet potatoes, peeled and cut into 3/4-inch cubes; Kosher salt; 1 stick unsalted butter (4 ounces; 115g), cubed and slightly softened; 1 cup (8 ounces) sour cream (see note); 1 cup (240ml) heavy cream; 6 thin slices bacon, diced; 1 1/2 cups (180g) panko bread crumbs; 1/4 cup thinly sliced scallions, white and light-green parts only; 6 ounces (170g) grated cheddar cheese