# Classic Shepherd's Pie (Lamb)

Shepherd's pie is a savory lamb and vegetable filling under a blanket of buttery mashed potatoes, baked until golden. It is one of the great comfort foods, and the proper version is made with lamb, as a shepherd would have.

The filling gets its depth from browned meat, tomato paste and Worcestershire, and the potato top crisps at the peaks. Make it once and it becomes a staple for cold nights.

- Total time: 1 h 25 min (prep 25 min, cook 1 h)
- Serves: 6
- Per serving (estimated): 470 kcal, 27 g protein
- Cuisine: British. Category: Main course.

## Ingredients

- 600 g ground lamb
- 900 g Yukon Gold potatoes, peeled and cut into chunks
- 3 tbsp butter, divided
- 1/2 cup whole milk, warm
- 1 tbsp olive oil
- 1 large onion, diced
- 2 carrots, diced
- 2 cloves garlic, minced
- 2 tbsp tomato paste
- 2 tbsp all-purpose flour
- 300 ml beef or lamb stock
- 1 tbsp Worcestershire sauce
- 1 tsp dried thyme
- 1 cup frozen peas
- 1 1/2 tsp salt, divided
- 1/2 tsp black pepper

## Method

1. Put the potatoes in a large pot, cover with cold water by 1 inch (2.5 cm) and add 1 teaspoon salt. Bring to a boil, then simmer 15 to 18 minutes, until a knife slides in with no resistance.
2. While the potatoes cook, heat the oil in a 12-inch (30 cm) oven-safe skillet over medium-high heat. Brown the lamb 6 to 8 minutes, breaking it up, until no pink remains. Spoon off all but 1 tablespoon of fat.
3. Add the onion and carrots and cook 5 minutes until the onion is soft. Add the garlic, tomato paste and thyme and cook 1 minute until the paste darkens.
4. Sprinkle the flour over the filling and stir 1 minute. Pour in the stock and Worcestershire, scraping up browned bits. Simmer 6 to 8 minutes until thick like gravy. Stir in the peas, 1/2 teaspoon salt and pepper.
5. Heat the oven to 400°F (200°C). Drain the potatoes well and return them to the warm pot for 1 minute to steam off moisture.
6. Mash the potatoes with 2 tablespoons butter, the warm milk and the remaining salt until smooth. Spoon over the lamb and spread to the edges, then rake the top with a fork.
7. Dot with the remaining 1 tablespoon butter. Bake on a baking sheet 25 minutes, until the filling bubbles at the edges and the peaks are golden and the center reads 165°F (74°C). Rest 10 minutes before serving.

## Why it works

- Browning the lamb until it is truly browned creates Maillard flavor and a savory base for the whole filling.
- Tomato paste cooked for a minute loses its raw edge and adds umami, which gives the gravy a meaty depth.
- Flour cooked in the fat thickens the stock into a gravy that holds the filling together under the potatoes.
- Steaming drained potatoes in the hot pot removes extra water, so the mash is fluffy rather than gluey.
- Raking the top with a fork creates peaks that brown and crisp in the oven.

## The science

- **Starchy vs waxy potatoes.** Yukon Golds sit between floury and waxy. They mash into a creamy texture without turning gluey, because their moderate starch holds up to mashing. Overworking very starchy potatoes ruptures the granules and releases sticky starch.
- **Thickening gravy.** Flour starch swells in hot liquid and thickens it as it simmers. Cooking the flour in fat first removes its raw taste and makes the gravy smooth. The filling needs to be thick, or the mash will sink into it.

## Tips

- Make the filling thick; a loose filling lets the mash sink and bake into a soggy layer.
- Warm the milk and butter before mashing so the potatoes stay hot and fluffy.
- Bake on a baking sheet to catch drips and keep your oven clean.

## Mistakes to avoid

- Adding cold milk to hot potatoes, which cools the mash and makes it heavy; warm it first.
- Skipping the browning step, which leaves the filling bland and gray; let the lamb brown.
- Leaving the filling too thin, which makes the pie collapse when sliced; simmer until thick.

## Variations and swaps

- Top with a mix of mashed potato and parsnip for a sweeter crust.
- Make cottage pie by using ground beef instead of lamb.
- Stir 1/2 cup grated cheddar into the mash for a cheesy crust.
- Swap ground lamb for ground beef (that makes it a cottage pie) cooked to 160°F (71°C).
- Swap frozen peas for frozen corn or green beans.
- Swap beef stock for vegetable stock and add a teaspoon of soy sauce for savoriness.

## Storage

Cool and refrigerate within 2 hours and eat within 3 to 4 days. Freeze portions up to 3 months and reheat in a 350°F (175°C) oven until the center reaches 165°F (74°C).

## FAQ

**What is the difference between shepherd's pie and cottage pie?**

Shepherd's pie is made with lamb, while cottage pie uses beef. The mashed potato topping and the method are otherwise the same.

**Can I make shepherd's pie ahead of time?**

Yes. Assemble it, cover and refrigerate up to 24 hours before baking, adding 10 to 15 minutes to the bake time. You can also freeze it unbaked.

**Why is my shepherd's pie watery?**

The filling was not simmered long enough to thicken, or the potatoes were not drained well. Reduce the gravy until thick, and steam the drained potatoes dry.

**What temperature should shepherd's pie be?**

Ground lamb is safe at 160°F (71°C), and a fully assembled pie should be 165°F (74°C) in the center when baked. When reheating leftovers, bring the pie to 165°F (74°C) too.

**Do I need to use an oven-safe skillet?**

No. Build the filling in any pan and transfer it to a 9 by 13 inch (23 by 33 cm) baking dish before topping with the potatoes.

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Source: https://cookingscientist.com/recipes/shepherds-pie (Cooking Scientist). Learn the science of cooking in the Cooking Scientist app for iPhone and iPad: https://apps.apple.com/app/id6830326846