How to Make It
Preheat the oven to 350°. In a large nonstick skillet, heat the olive oil over moderately high heat. Add the potatoes and cook, stirring occasionally, until golden brown, about 7 minutes. Drain on paper towels and season with salt and pepper.
Meanwhile, heat a 10-inch cast-iron skillet over moderately high heat. Add the ground lamb, season with salt and pepper and cook, stirring to break up the meat, until browned, about 5 minutes. Drain off all but 1 tablespoon of fat from the pan. Add the onion and cook, stirring frequently, until softened, about 3 minutes. Add the garlic, the chopped mint and the oregano and cook, stirring, for 1 minute. Add the flour and cook over moderate heat, stirring, for 2 minutes. Add the chicken stock, season with salt and pepper and bring to a boil. Stir in the peas and remove from the heat. Spread the meat mixture in an even layer and arrange the potatoes on top in overlapping slices. Top with the feta.
Bake the pie for about 15 minutes, until the cheese is lightly browned and the meat is bubbling. Let cool slightly, then garnish with mint leaves and serve.