Ingredients

• 3 pounds Yukon Gold potatoes
• 1 tablespoon kosher salt
• 0.25 cups milk
• 3 tablespoons salted butter , divided
• 1 cup shredded white Cheddar cheese
• 0.25 cups sour cream
• 1 large egg yolk
• 2 teaspoons kosher salt , divided
• 1 teaspoon ground black pepper , divided
• 1 tablespoon olive oil
• 1 cup diced onion
• 1 cup diced carrot
• 1 pound ground lamb
• 1 pound ground beef sirloin
• 3 tablespoons all-purpose flour
• 1 teaspoon finely chopped fresh rosemary
• 1 teaspoon finely chopped fresh thyme
• 1 cup beef stock
• 1 tablespoon tomato paste
• 1 tablespoon Worcestershire sauce
• 1 cup frozen green peas
• 1 tablespoon chopped fresh parsley , or to taste

Instructions

1. 1 Place potatoes in large saucepan and add enough water to cover by 2 inches. Stir in 1 tablespoon salt and place pot over medium-high heat; bring to a boil. Cook until potatoes are fork tender, about 10 minutes. Turn off the heat and drain.
2. 2 Return potatoes to the hot pan and set over the same burner. Add milk and 2 tablespoons butter; allow butter to melt from the residual heat. Mash potatoes with a potato masher until smooth. Stir in Cheddar cheese, sour cream, egg yolk, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Set aside while you prepare the filling.
3. 3 Preheat the oven to 375 degrees F (190 degrees C). Grease a 9x13-inch casserole dish.
4. 4 Heat olive oil and remaining 1 tablespoon butter in a large skillet over medium-high heat. Add onion and carrot and cook, stirring constantly, until onion begins to turn translucent, about 5 minutes.
5. 5 Add lamb and beef and cook, crumbling with a spoon and stirring often until browned, about 5 minutes. Sprinkle meat mixture with flour, remaining salt and pepper, rosemary, and thyme. Cook, stirring constantly, for 2 minutes.
6. 6 Add beef stock, tomato paste, and Worcestershire; cook, scraping any flavorful bits from the bottom of the skillet. Bring mixture to a simmer. Cook until thickened and vegetables are tender, about 8 minutes. Stir in peas. Transfer mixture to the prepared casserole dish and top with the prepared mashed potatoes.
7. 7 Bake in the preheated oven until golden and bubbly around the edges, 25 to 30 minutes. Sprinkle with parsley and serve.

Nutrition per serving