Shepherd's Pie

Traditional shepherd's pie is made with lamb (beef version is technically cottage pie) — either way, the trick is cooking the filling down until it's thick enough to hold its shape under the potatoes.

Instructions

1. 1

   Place the potatoes in a large pot, cover with cold salted water, and bring to a boil. Cook until fork-tender, 15–18 minutes. Drain thoroughly.

2. 2

   Mash the potatoes with 4 tablespoons butter and the warm milk until smooth and creamy. Season with salt and pepper, and stir in the egg yolk if using for extra richness and color. Set aside.

3. 3

   Preheat the oven to 400°F (200°C).

4. 4

   Heat the olive oil in a large, deep oven-safe skillet over medium-high heat. Add the ground lamb or beef and cook, breaking it up with a spoon, until browned, 7–8 minutes. Drain excess fat, leaving about a tablespoon.

5. 5

   Add the onion, carrots, and celery to the pan and cook, stirring occasionally, until softened, 7–8 minutes.

6. 6

   Add the garlic and tomato paste and cook, stirring, for 2 minutes.

7. 7

   Sprinkle the flour over the mixture and stir constantly for 1–2 minutes.

8. 8

   Pour in the beef broth and Worcestershire sauce, stirring to combine, and add the thyme. Simmer, stirring occasionally, until the filling has thickened enough that a spoon dragged through it leaves a clear trail, 10–12 minutes — this is important, since a runny filling will make the potato topping sink and slide during baking.

9. 9

   Stir in the frozen peas and season with salt and pepper. Remove from heat.

10. 10

    If your skillet isn't going straight into the oven, transfer the filling to a 9x13-inch baking dish. Spread the mashed potatoes evenly over the top, right to the edges, sealing the filling underneath (this prevents it from bubbling up through gaps and burning).

11. 11

    Use a fork to rough up the surface of the potatoes into peaks and ridges — this creates more surface area to brown and crisp.

12. 12

    Dot the top with the remaining 2 tablespoons butter, cut into small pieces.

13. 13

    Bake for 25–30 minutes, until the filling is bubbling at the edges and the potato topping is golden brown in spots. For extra browning, broil for the final 2–3 minutes, watching closely.

14. 14

    Let rest for 10 minutes before serving.