Twice Baked Potato Casserole

INGREDIENTS

• 8 tablespoons (1 stick) plus 1 tablespoon unsalted butter, at room temperature
• 1 cup sour cream
• 1 1/2 teaspoons freshly ground black pepper
• 1/2 cup finely chopped green onions
• 10 large russet baking potatoes (about 7 pounds total)
• 2 teaspoons salt
• 3/4 pound mild Cheddar, grated (3 cups)
• 3/4 pound bacon, cooked until crisp and crumbled
• 3 eggs, lightly beaten
• 1/2 cup heavy cream
• 1/2 pound sharp white Cheddar, cut into 1/2-inch cubes