Potato Leek Frittata

1 lb yukon gold potatoes, cooked, cubed
2 tablespoons ghee, clarified butter, bacon fat, or olive oil
1 medium leek, white and light green parts, halved length-wise, rinsed well, and sliced
8 large eggs
1/2 teaspoon salt + black pepper
1 cup shredded cheese (sharp or smoked cheddar, smoked gouda, asiago, are all good choices)

1. Heat a 10 inch well-seasoned cast iron pan over medium heat. Add fat of your choice and potatoes. Season potatoes with salt. Cook until the potatoes are lightly browned, about 5 minutes. Add in the leeks, season with salt again, and continue cooking until leeks are soft, another 5 minutes or so. Reduce heat to low.
2. Heat oven to 350°F. Beat the eggs, salt, and pepper in a bowl. Stir in cheese.
3. Pour egg mixture over the potatoes and cook, undisturbed for about 5 minutes.
4. Place pan in oven and bake for about 15 minutes. When it’s puffy and golden, it’s done.
5. Serve hot or at room temperature.