Step 1

Arrange a rack in the middle of the oven and heat the oven to 325°F. Meanwhile, cut 1 1/2 pounds boneless leg of lamb and 1 1/2 pounds boneless beef chuck roast into 1-inch pieces, discarding any separable fat from the meat and discarding it. Season the lamb and beef pieces and lamb chop (leave intact) all over with 1 teaspoon kosher salt and 1 teaspoon black pepper. Halve and thinly slice 2 medium onions.

Step 2

Heat 1 tablespoon of vegetable oil in a large Dutch oven over medium-high heat until shimmering. Add one handful of the cut meat and sear until browned all over, about 5 minutes. Transfer to a large bowl and continue browning the remaining meat the same way, reducing the heat if the bits on the bottom of the pot begin to burn. Sear the shoulder chop on both sides until browned, then add to the bowl.

Step 3

Add the onions to the pot and cook over medium heat, stirring occasionally, until tender and well browned, about 8 minutes. Adjust the heat as needed to prevent the onions from burning. Add 1 cup Guinness Irish Stout and simmer, scraping up the browned bits from the bottom of the pan, until the stout has reduced by half, about 2 minutes. Pour the onion and beer mixture into the bowl with the browned meat and turn off the heat.

Step 4

Peel 1 large russet potato and cut crosswise into 1/2-inch thick slices. Arrange the slices in a single layer on the bottom of the Dutch oven. Pour the beef, lamb, and onion mixture back into the pot over the potatoes. Do not stir.

Step 5

Peel 2 large carrots and cut crosswise on a slight diagonal into 1 1/2-inch wide pieces. Peel and coarsely chop 1 large parsnip, if using. Add the carrots, parsnip, 4 fresh thyme sprigs, and 1 bay leaf to the pot. Pour in enough homemade or low-sodium beef broth to just cover everything. Cover and bake until the meat is fairly tender, about 1 1/2 hours.

Step 6

Peel and cut 1 pound Yukon gold potatoes into 1/2-inch chunks. Remove the pot from the oven. Skim off any fat that has surfaced on the top of the stew and discard. Put the Yukon gold potatoes on top of the stew but don’t stir them in. Cover with the lid slightly ajar. Bake until the meat and potatoes are very tender, about 30 minutes.

Step 7

Stir the stew gently to break up the potatoes at the bottom of the pot. Remove the shoulder chop bones and break up the chop meat with a fork, if necessary. Discard the bay leaf and thyme stems. Taste and season with Worcestershire sauce, kosher salt, and black pepper as needed. Garnish with additional chopped thyme leaves, if desired.