Preheat your oven to 375 degrees Fahrenheit. This sets the stage for perfectly baked Shepherds Pie.
In a large, deep skillet, heat 1 tablespoon vegetable oil over medium-high heat. Once hot, add 1 cup carrots, 1 cup celery, and 1 ½ cup onion. Sauté these veggies until they soften, about 5 minutes, allowing their flavors to meld.
Next, add 1 pound lean ground beef to the skillet. Use a wooden spoon to break it apart as it cooks. You want it thoroughly browned with no pink remaining. This should take about 5 to 7 minutes. Add 2 teaspoons minced garlic in the last minute of cooking for extra flavor.
Now, whisk together 1 ½ cup beef broth and 1 tablespoon cornstarch in a bowl. Pour this mixture into the skillet along with ⅓ cup tomato paste, 3 tablespoons Worcestershire sauce, ¼ teaspoon dried thyme, ¼ teaspoon dried oregano, 1 teaspoon dried parsley, 1 teaspoon salt, and ¼ teaspoon black pepper. Stir well and let it simmer for 5 minutes until the sauce thickens. Add in 1 cup frozen peas and stir to combine.
While the filling simmers, prepare the mashed potatoes. In a large pot, add the peeled and diced 2 pounds russet or golden potatoes and cover them with cold water. Season with a couple of pinches of kosher salt. Bring to a boil over high heat and then reduce to a rolling boil. Cook until the potatoes are tender, about 12 to 15 minutes.
Drain the potatoes and return them to the pot. For the creamiest texture, you can either run them through a potato ricer or use a hand masher. Add 2 tablespoons butter, warm ½ cup half and half, and 5.2 ounces Boursin cheese to the potatoes. Mash until creamy, tasting for seasoning, adding more salt and pepper if needed.
Spread the creamy potatoes evenly over the top of the meat and vegetable mixture in the skillet.
Bake the Shepherds Pie uncovered for 25 to 30 minutes until the edges are bubbling and golden. This gives it that perfect crust.
Once done, sprinkle with fresh chopped parsley for a pop of color and flavor before serving. Enjoy your Homemade Shepherds Pie!
