3 pounds
russet potatoes, peeled, cut into 2-inch pieces
1 cup
unsalted butter, softened
1 cup
whole milk
1 teaspoon
granulated garlic powder
1 teaspoon
kosher salt
½ teaspoon
freshly cracked black pepper
For the Filling
2 pounds
90/10 ground beef or ground lamb
1 ½ teaspoons
kosher salt
1 tablespoon
extra-virgin olive oil
1 small
yellow onion, finely chopped
2 large
carrots, peeled and finely diced
1 cup
finely chopped fennel, from 1 small bulb
2
garlic cloves, minced
2 tablespoons
all-purpose flour
2 tablespoons
tomato paste
2 cups
beef broth
½ teaspoon
freshly cracked black pepper, plus more for serving
1 teaspoon
finely chopped fresh thyme, plus more for serving
1 teaspoon
finely chopped fresh rosemary
1 cup
frozen peas
Method
Preheat the oven to 400°F with a rack in the center position.
Fill a large pot with water and salt it. Add the potatoes and bring to a boil over high heat. Cook until fork tender, about 15 minutes. Drain.
Using the same pot, combine the butter and milk over medium-low heat. Cook, stirring, until the butter is melted, about 2 minutes. Using a potato ricer, rice the potatoes over the hot butter mixture. (Alternatively, mash the potatoes directly into the liquid, taking care not to overwork them.) Season with the garlic powder, salt and pepper.
Make the filling. In a large skillet over medium-high heat, add the ground beef and season with 1 teaspoon of the salt. Cook, breaking up the meat with a wooden spoon, until cooked through, about 8 minutes. Drain any excess grease and transfer to a plate.
Using the same skillet, reduce the heat to medium and add the olive oil. Once the oil is glistening, add the onions, carrots, and fennel. Season with remaining ½ teaspoon of salt and cook, stirring often, until the vegetables are softened, about 5-7 minutes. Stir in the garlic and cook until fragrant, about 2 more minutes more.
Stir in the flour and tomato paste and cook, stirring continuously, until the tomato paste has darkened, about 1 minute. Stir in the beef stock, pepper, thyme, and rosemary and bring to a simmer. Add the browned beef and any collected juices and frozen peas and simmer, stirring occasionally until sauce has thickened and liquid is mostly absorbed, about 10 minutes.
Transfer the filling to a 9x13-inch baking dish and spread out evenly. Top with the mashed potatoes, and smooth out into an even layer using the back of a spoon. Bake until the filling is bubbling and potatoes are golden brown, about 20 minutes.
Top with additional pepper and thyme and let cool for 15 minutes before serving.