Kohlrabi, a member of the turnip family, is rich in potassium and vitamin C. Its earthy, slightly sweet flavor makes it a great substitute for potatoes in dishes like potato salad. For this shepherd’s pie, roasting the kohlrabi adds extra flavor and dries the vegetable out to ensure a creamy, not watery, topping. As it’s roasting, the ground lamb is simmered with vegetables, thyme, tomato paste, wine, and beef broth until it’s a thick, saucy filling. The roasted kohlrabi is then puréed and spread on top of the filling, before the whole dish is baked until bubbly and browned.
Game plan: The filling can be made up to 1 day ahead, cooled to room temperature, and refrigerated in an airtight container. Reheat the filling before proceeding with the recipe.
1/4 teaspoon freshly ground black pepper, plus more as needed
2 medium carrots, peeled and small dice
1 medium yellow onion, small dice
2 medium garlic cloves, minced
3/4 teaspoondried thyme
2 tablespoonstomato paste
1/2 cup dry red wine
2 tablespoons all-purpose flour
2 cups low-sodium beef broth
1 tablespoonWorcestershire sauce
To finish the topping and assemble:
6 tablespoons unsalted butter (3/4 stick), at room temperature
Freshly ground black pepper
2 large egg yolks
1 cup frozen peas
For the kohlrabi:
Heat the oven to 425°F and arrange a rack in the upper third.
Trim the stem ends and any stalks or greens from the kohlrabies. Using a vegetable peeler, peel the skin and fibrous inner layer until you reach the white flesh. Cut the flesh into 1-inch cubes and place in a large bowl.
Add the oil, salt, and pepper and toss to combine. Transfer to a baking sheet and arrange in an even layer. Roast until knife tender, about 30 minutes. Meanwhile, make the filling.
For the filling:
Heat the oil in a large heavy-bottomed pot or Dutch oven over medium-high heat until shimmering. Add the lamb, 1 teaspoon of the salt, and the measured pepper. Cook, using a wooden spoon to break up the lamb into small pieces, until the meat is completely cooked through and most of the moisture has evaporated, about 7 to 10 minutes. Remove with a slotted spoon to a medium bowl; set aside.
Reduce the heat to medium. Add the carrots, onion, garlic, thyme, and remaining 1/2 teaspoon of salt to the pot. Season with pepper and cook, stirring occasionally, until the vegetables are softened and starting to brown, about 4 minutes. Return the lamb and any accumulated juices to the pot.
Add the tomato paste and stir to coat the lamb and vegetables. Cook, stirring occasionally, until the tomato paste is no longer raw-tasting, about 2 minutes. Add the wine and cook, stirring occasionally, until it has completely evaporated, about 1 minute. Sprinkle in the flour and cook, stirring occasionally, until it’s no longer raw-tasting, about 1 minute.
Add the beef broth and Worcestershire, scrape up any browned bits that have accumulated on the bottom of the pot, and bring to a boil. Reduce the heat to medium low and simmer, stirring occasionally, until the filling has thickened, the liquid is reduced by half, and the flavors have melded, about 20 minutes. Taste and season with additional salt and pepper as needed; keep warm.
To finish the topping and assemble:
Place the roasted kohlrabi in the bowl of a food processor fitted with a blade attachment. Add the butter and process until smooth, about 2 minutes. Taste and season with salt and pepper as needed. Add the egg yolks and process until just incorporated; set aside.
Add the peas to the filling and stir to combine. Transfer the filling to a 13-by-9-inch baking dish and spread it into an even layer.
Drop the kohlrabi topping in large spoonfuls over the filling and spread it into an even layer. Bake until the shepherd’s pie is bubbling and starting to brown around the edges, about 25 minutes. Remove the dish to a wire rack and let it sit for 5 minutes before serving.