- 4 medium russet potatoes, 2 pounds, peeled and cut into 1-inch pieces
- 7 tablespoons unsalted butter, divided
- 1/2 cup half and half
- 1 teaspoon salt, divided
- 1/2 teaspoon ground black pepper, divided
- 1 large onion, chopped
- 3 carrots, finely chopped
- 3 garlic cloves, minced
- 1 teaspoon chopped fresh thyme
- 1 pound ground lamb
- 1 pound 93% lean ground beef
- 1/4 cup tomato paste
- 5 teaspoons Worcestershire sauce
- 1 2/3 cup low sodium beef broth
- 3/4 cup frozen peas
- 6 ounces aged Irish cheddar cheese, grated
- Preheat the oven to 350°F. Coat an 8-cup baking dish with cooking spray (if the dish is nonstick, do not use the nonstick spray).
- In a large saucepan combine the potatoes with enough cold water to cover by 2-inches. Bring to a boil over medium-high heat and cook until tender, 16 to 18 minutes; drain, and return to the saucepan. In a small saucepan heat the milk over medium-high heat until hot. Add 6 tablespoons butter, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook until the butter melts. Pour the milk mixture into the saucepan with the potatoes and mash until smooth; reserve.
- Heat a large nonstick skillet over medium-high heat and add the ground lamb and ground beef. Cook, breaking into smaller pieces with a wooden spoon, until no longer pink, 8 to 9 minutes. Transfer the meat to a bowl with a slotted spoon and reserve. Pour off all but 2 tablespoons fat from the skillet and return to the stove over medium heat. Stir in the onion, carrots, and thyme; cook, stirring occasionally, until the vegetables are tender but not brown, 8 to 10 minutes. Add the lamb and beef, tomato paste, and Worcestershire sauce to the skillet and cook, stirring, 1 minute. Pour in the broth, bring the mixture to a boil and cook until liquid is almost evaporated, about 8 minutes. Stir in the peas and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper and cook 1 minute. Transfer to the prepared baking dish. Sprinkle the cheese over the filling in an even layer.
- Spread the potatoes in an even layer over the cheese and with make a crosshatch design on the top with the tines of a fork. Melt the remaining 1 tablespoon butter and lightly brush the potatoes.
- Transfer to the oven and bake until the filling is bubbling and the top begins to brown, 30 to 32 minutes.