Instructions

1. Preheat oven to 350°F. In a shallow bowl, mix 1/2 cup flour, 1/2 teaspoon salt and 1/2 teaspoon pepper. Add lamb, a few pieces at a time, and toss to coat. Heat oil over medium-high heat in a Dutch oven. Brown lamb in batches and remove from pan. In same pan, add carrots and onion. Cook and stir until crisp-tender. Stir in remaining 1 tablespoon flour until blended before gradually whisking in the stock. Bring to a boil.
2. Add potatoes, thyme, bay leaf, Worcestershire sauce, tomato paste, salt, pepper, and lamb; return to a boil, then reduce heat. Simmer, uncovered, until sauce is thickened and lamb is tender, about 30 minutes. Remove and discard thyme sprig and bay leaf. Stir in mint. Transfer mixture to a greased 9-in. deep-dish pie plate.
3. Whisk egg yolk; brush around edge of pie plate to help pastry adhere to pan. On a lightly floured surface, unfold both pastry sheets, and stack them on top of each other. Roll pastries thinner to fit across pie dish easily, if needed. Carefully place over pie dish and filling, then trim off excess. Using a fork, press crust firmly onto rim of pie plate to seal edges. Brush top with remaining egg and cut slits in top. Place on rimmed baking sheet and bake until golden brown, 35-40 minutes. Let stand 10 minutes before serving.