Best Shepherd's Pie

Preheat oven to 400°. In a medium saucepan, cover potatoes with water by 1/2"; season with 1 tablespoon salt. Bring to a boil over high heat. Cook until potatoes are fork-tender, 12 to 15 minutes. Drain potatoes; set aside in colander.

In same pot over medium-low heat, cook half-and-half and butter, stirring until butter is melted. Return potatoes to pot. Mash potatoes with a potato masher or a fork. Stir in 1 tablespoon parsley; season with salt and pepper. Remove from heat.

Meanwhile, in a large skillet over medium-high heat, heat oil. Add beef; season with 2 teaspoons salt and 1/2 teaspoon pepper. Break up beef with a wooden spoon and cook until crumbled and no longer pink, 6 to 8 minutes. Using a slotted spoon, transfer beef to a plate. Pour off all but 2 tablespoons beef drippings.

In same skillet over medium heat, cook onion and carrots, stirring, until onions begin to soften, 5 to 6 minutes. Add garlic, rosemary, and thyme and cook, stirring, until fragrant, about 2 minutes more. Return beef and accumulated juices to skillet; stir in tomato paste. Cook, stirring, until tomato paste turns dark red, 3 to 4 minutes. Add wine and cook, stirring, until almost completely evaporated, 2 to 3 minutes. Stir in broth and Worcestershire and bring to a simmer. Sprinkle with flour and cook, stirring occasionally, until sauce is thickened, about 5 minutes. Stir in corn and peas.

Pour beef mixture into a 13" x 9" pan and dollop mashed potatoes on top. Lightly spray a rubber spatula with cooking spray and spread potatoes over beef mixture. Sprinkle with Parmesan; season with a pinch of pepper.

Bake shepherd’s pie until beef mixture is bubbling, about 25 minutes. Remove from oven. Place a rack in upper third of oven and turn broiler to high. Broil until top begins to brown, 1 to 2 minutes.

Sprinkle with remaining 1 tablespoon parsley. Let cool 10 minutes before serving.