Spiced Lamb and Potato Pie

Name: Spiced-Lamb and Potato Pie
Ingredients: 1/4 cup extra-virgin olive oil; 1 pound baking potatoes, peeled and very thinly sliced; Salt; Freshly ground pepper; 1 pound ground lamb; 1 small onion, chopped; 2 garlic cloves, chopped; 1 tablespoon chopped mint, plus mint leaves for garnish; 1 teaspoon dried oregano; 2 tablespoons all-purpose flour; 1 cup chicken stock or low-sodium broth; 1 cup frozen peas, thawed; 5 ounces feta cheese, crumbled (1 cup)