Mom's Shepherd's Pie

This is a true shepherd’s pie, the authentic version made with lamb rather than the beef-based dish that is really called cottage pie. The traditional British way to use up Sunday’s leftover lamb roast, this recipe turns scraps into a whole new meal with nothing more than an onion, a pepper, some mashed potatoes, and rosemary.

The cornstarch slurry is what separates this recipe from the watery, slumped disasters that people sometimes call shepherd’s pie. Softening the cornstarch in cold water first prevents lumps when it hits the hot pan. Stirred into the simmering lamb and vegetables, it tightens the liquid into a proper gravy that holds the filling together under the potato crust rather than leaking out the sides when you scoop a serving.

The potato crust should be at least a half inch thick. Any thinner and it cracks during baking, letting the gravy bubble up over the top. Dotting with butter before it goes in the oven is the classic move that gives the top its golden, toasty finish. Dusting with paprika makes the color deeper, and a sprinkle of parmesan takes it toward gratin territory.

Chef Tips

• Trim the lamb well and cube it small, about half-inch pieces. Big chunks of leftover meat are chewy in the gravy; small cubes disappear into tender bites.
• Use mashed potatoes on the stiff side, not fluffy and whipped. Loose mashed potatoes slump into the filling and sink rather than forming a proper crust.
• Score the top of the potato layer with a fork in a crosshatch pattern. Those peaks brown first and give the finished pie an attractive ridged surface.
• Rest the pie 10 minutes before serving. Straight from the oven, the gravy is molten and the slice falls apart.

Variations

• For true British authenticity, stir a tablespoon of Worcestershire sauce and a splash of red wine into the gravy.
• Add a cup of frozen peas and corn during the last five minutes of the lamb simmer for a more classic pub version.
• Top the mashed potatoes with grated sharp cheddar in the last 10 minutes of baking for a richer, Lancashire-style crust.