Start to finish: 1 hour, 15 minutes
2 pounds russet potatoes, peeled and cut into 1-inch pieces
Salt and pepper
1/2 cup milk
1 large egg
4 tablespoons unsalted butter, melted, plus 2 tablespoons unsalted butter
2 carrots, peeled and chopped
1 onion, chopped fine
1 1/2 pounds of 93 percent lean ground beef
2 tablespoons tomato paste
2 garlic cloves, minced
2 teaspoons minced fresh thyme or ½ teaspoon dried
2 tablespoons all-purpose flour
1 1/2 cups chicken broth
2 teaspoons Worcestershire sauce
1 cup frozen peas
Cover potatoes with water in large saucepan. Add 1 tablespoon salt, bring to simmer over medium-high heat, and cook until potatoes are tender, 8 to 10 minutes. Drain potatoes and return them to saucepan. Using potato masher, mash potatoes until smooth. Whisk milk and egg together, then stir into potatoes along with melted butter, 1 teaspoon salt, and 1/2 teaspoon pepper; cover and set aside.
Heat 10-inch cast-iron skillet over medium heat for 3 minutes. Melt remaining 2 tablespoons butter in skillet. Add carrots, onion, and 3/4 teaspoon salt and cook until softened, about 5 minutes. Add beef and cook, breaking up meat with wooden spoon, until no longer pink, 8 to 10 minutes.
Stir in tomato paste, garlic, and thyme and cook until fragrant, about 1 minute. Stir in flour and cook for 1 minute. Slowly stir in broth and Worcestershire, scraping up any browned bits and smoothing out any lumps. Bring to simmer and cook, stirring occasionally, until mixture has thickened slightly, about 10 minutes. Off heat, stir in peas and season with salt and pepper to taste.
Adjust oven rack 5 inches from broiler element and heat broiler. Transfer potato mixture to 1-gallon zipper-lock bag and snip off 1 corner to create 1-inch opening. Pipe mixture in even layer over filling. Smooth topping with back of spoon, then use tines of fork to make ridges on surface. Place skillet in rimmed baking sheet and broil until topping is golden brown and crusty, 5 to 10 minutes. Let casserole cool for 10 minutes before serving.
Nutrition information per serving: 442 calories; 183 calories from fat; 21 g fat (11 g saturated; g trans fats); 139 mg cholesterol; 379 mg sodium; 36 g carbohydrate; 5 g fiber; 6 g sugar; 31 g protein.
For more recipes, cooking tips and ingredient and product reviews, visit https://www.americastestkitchen.com. Find more recipes like Shepherd’s Pie in “Cook It In Cast Iron .”
America’s Test Kitchen provided this article to The Associated Press.