• Preheat the oven to 375 degrees Fahrenheit.
• In a large, deep skillet, heat the oil over medium-high heat and cook the carrots, celery, and onion until softened, about 5 minutes.
• Add the beef and cook until thoroughly browned and no pink remains. Break it up into pieces as it cooks. Add the minced garlic and cook for 1 additional minute.
• Whisk together beef broth and cornstarch. Add it to the skillet, along with the tomato paste, Worcestershire sauce, herbs, and salt and pepper. Stir in the frozen peas and cook for 5 minutes, until the sauce has thickened.

Mashed Potatoes

• Add the peeled and diced potatoes to a large pot and fill with cold water until the potatoes are covered. Add 2-3 large pinches of kosher salt.
• Place the pot over high heat and bring to a boil. Reduce heat to maintain a rolling boil and cook until tender, about 12-15 minutes.
• Drain the potatoes into a colander. Return the potatoes to the pot and either run them through a potato ricer or use a hand masher to mash them well. Add the butter, warm half and half, and Boursin cheese to the potatoes and mash until creamy. Taste and season with salt and pepper if needed.
• Spread the potatoes evenly over the top of the meat mixture.
• Bake the Shepherd's pie uncovered for 25-30 minutes until the edges are bubbling. Sprinkle with fresh chopped parsley and serve.