Step 1

Add the leeks, chopped onions, and one rosemary sprig into the base of the slow cooker. Sprinkle cornstarch over the top and toss to coat.

Step 2

Generously season the lamb roast with salt and pepper. Place the roast into the crockpot and pour stock and water until it reaches at least halfway to 2/3 up the sides of the lamb. Add additional water (or stock) if needed.

Step 3

Slow cooker on low for 8 hours or high for about 5 hours. Cooking times may vary depending on the size of your roast. Cook until the lamb is tender and to your liking.

Step 4

Once the lamb is tender enough to easily separate with a fork, remove it from the slow cooker and place it in a roasting pan. Roast in a 375℉ oven for 15-20 minutes to brown. Remove from the oven and let rest for 10-20 minutes.

Step 5

While the lamb is browning, make the gravy. Transfer the cooking liquid to a fat separator if you have one. A baster works well too. Then, pour the juices into a saucepan.

Step 6

Create a slurry by mixing 1 tablespoon of cornstarch with 1 tablespoon of water and then add to the saucepan. The onions and leeks can be added to the gravy if desired. Bring the gravy to a boil, then reduce to a simmer and cook until reduced and it reaches the desired thickness. Serve with lamb.