If you can't find or don't like lamb, use 2 pounds of non-lean ground beef instead of the mix of lamb and beef.

• Boil the potatoes in salted water for 14 minutes. Drain and place in a large mixing bowl. Mash lightly and use a hand-mixer to incorporate the milk, egg, and sour cream until the potatoes are smooth. Set aside.

• Place a large skillet over medium-high heat and when heated, add the ground lamb. Sprinkle with salt and pepper and stir, crumbling the lamb. Cook for 4–6 minutes. Remove the meat, but not any fat, and place in a bowl. Add the ground beef to the skillet and cook for 3–4 minutes, stirring and breaking the meat apart. Add it to the bowl with the lamb. Drain off all but 2 tablespoons of the fat and discard.

• Add the onion and carrot to the pan. Cook for 5–7 minutes. Stir in the garlic and cook for 1 minute. Sprinkle the flour over the vegetables and toss to coat.

• In a small bowl combine the chicken broth, vinegar, Worcestershire sauce, thyme, and mustard powder. Stir it into the skillet. Bring to a boil and thicken slightly. Stir in the meat and the peas. Remove from the heat and smooth out the mixture.

• Preheat the broiler and place a rack in the middle of the oven. Spoon the whipped potatoes over the contents in the skillet. Sprinkle paprika over the potatoes. Place in the oven and broil. Check every 30 seconds and remove when the potatoes are golden brown. Rotate the skillet so the potatoes brown evenly. Remove from the oven and let it rest for 5 minutes before serving.

Cottage Pie versus Shepherd's Pie

The term “shepherd's pie” wasn't used until the 1870s, when people in the British Isles started eating potatoes. “Cottage pie” has been cited before 1800 and refers to a crust-covered pie filled with beef instead of lamb. On current menus, you're likely to find cottage pie referring to dishes with beef and shepherd's pie referring to dishes with lamb.