1/2 cup sour cream
2 ounces cream cheese
2 tablespoons butter, softened, divided
1 egg yolk
1/2 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
1 1/2 teaspoons olive oil
1 pound ground lamb
1 pinch salt and ground black pepper to taste
1 (16 ounce) can stewed tomatoes with juice, chopped
1 small onion, chopped
1 small carrot, peeled and chopped
1/2 cup peas
1 cup Irish stout beer (such as Guinness(R))
1 cube beef bouillon
1 tablespoon all-purpose flour
1 tablespoon Worcestershire sauce
3/4 cup shredded sharp Cheddar cheese
2 teaspoons chopped fresh parsley
2 teaspoons smoked paprika
Stir potatoes, sour cream, cream cheese, 1 tablespoon butter, egg yolk, 1/2 teaspoon salt, and 1/2 teaspoon black pepper together in a bowl until smooth. Heat olive oil in a cast iron skillet or nonstick pan over medium-high heat. Add ground lamb, reduce heat to medium, and cook, stirring frequently, until browned and crumbly, 4 to 5 minutes. Pour off excess grease and season lamb with salt and black pepper to taste. Stir tomatoes with juice, onion, and carrot into ground lamb; simmer until vegetables are tender, 5 to 10 minutes. Add peas, reduce heat to low, and cook, stirring frequently, until peas are warmed, 2 to 3 minutes. Heat beer in a saucepan over medium heat; add beef bouillon. Cook and stir beer mixture until bouillon is dissolved, about 5 minutes. Heat remaining 1 tablespoon butter in a separate pan over medium-low heat until sizzling. Whisk flour into butter until thick and paste-like, about 1 minute. Stir beer mixture and Worcestershire sauce into flour mixture until gravy is smooth and thickened, 2 to 3 minutes. Stir gravy into lamb mixture and simmer until mixture is thickened, at least 5 minutes. Set oven rack about 6 inches from the heat source and preheat the oven's broiler. Grease a 9x12-inch baking dish. Pour lamb mixture into the prepared baking dish. Carefully spoon mashed potatoes over lamb mixture, covering like a crust. Sprinkle Cheddar cheese, parsley, and paprika over mashed potatoes. Broil in the preheated oven until crust is browned and cheese is melted, 4 to 5 minutes. Cool for about 5 minutes before serving.