In the deep half of an 8-inch frittata pan over medium-high heat, melt 1 Tbs. of the butter. Add the potatoes, salt and pepper, cover with the shallow pan and cook, flipping the potatoes occasionally, until tender and browned, about 8 minutes. Transfer to a bowl.
In the deep half of a frittata pan over medium heat, melt 1 Tbs. of the butter. Add the leeks, salt and pepper and cook, stirring occasionally, until softened, 6 to 8 minutes. Transfer to a separate bowl.
In another bowl, whisk together the eggs and cream. Stir in the cheese, parsley, potatoes, salt, pepper and all but 2 Tbs. of the leeks.
In the deep half of the frittata pan over medium heat, melt 1/2 Tbs. of the butter. Add the egg mixture and cook until the eggs are just beginning to set, about 4 minutes, using a rubber spatula to gently lift the cooked edges and allow the uncooked eggs to flow underneath.
Meanwhile, in the shallow half of the frittata pan over medium heat, melt the remaining 1/2 Tbs. butter. Place the shallow pan upside down on top of the deep pan and flip the frittata into the shallow pan. Cook, covered, for 4 minutes. Remove the deep pan and cook until the eggs are completely set, 2 to 3 minutes more. Gently shake the pan to loosen the frittata and slide it onto a serving plate. Garnish with the reserved leeks.
Go to full version of