Step 1

Warm leftover mashed potatoes in the microwave or on the stove top, adding a splash of milk if needed to make them spreadable. If using instant potatoes, prepare them according to the directions on the package and season with salt and pepper to taste. Set aside.

Step 2

In a large skillet on medium-high heat on the stove-top, cook the ground lamb along with the onion and garlic until the meat is no longer pink. Drain off any excess fat.

Step 3

Add the tomato paste to the lamb mixture in the pan and cook 2 to 3 minutes.

Step 4

Add the carrots, peas, celery, beef stock, wine (or additional beef stock if using), Worcestershire sauce, and dried thyme. Bring to a boil.

Step 5

Reduce heat to low and simmer the mixture in the skillet, uncovered, until most of the liquid is evaporated. Taste the mixture and season with salt and pepper to taste.

Step 6

Transfer the lamb mixture to a slow cooker that has been sprayed with non-stick cooking spray.

Step 7

Spread the mashed potatoes over the top of the lamb mixture.

Step 8

Cover the slow cooker. Cook on LOW for 5 to 6 hours, or until you can see the lamb mixture bubbling around the edges of the mashed potato topping.

Step 9

Serve immediately straight from the slow cooker.