1-First, heat 2 tablespoons olive oil in a large skillet over medium-high heat. Add the chopped onion and cook until soft, about 5 minutes, to build a flavorful base.

2-Next, add 1.5 lbs (680g) ground beef or lamb along with 1 teaspoon each of dried parsley, rosemary, thyme, salt, and ½ teaspoon black pepper. Cook, breaking up the meat, until browned, about 6-8 minutes.

3-Stir in 2 tablespoons Worcestershire sauce and 4 cloves minced garlic; cook for 1 minute to enhance the aroma.

4-Sprinkle ¼ cup (30g) all-purpose flour and 2 tablespoons tomato paste over the mixture. Stir constantly until fully incorporated, about 1 minute, to thicken it up.

5-Pour in 1 cup (240ml) beef broth, scraping up any browned bits. Add 1 cup (150g) frozen mixed peas and carrots plus ½ cup (75g) frozen corn kernels. Bring to a boil, then simmer until thickened, about 5-7 minutes, and remove from heat.

6-Preheat your oven to 400°F (200°C). For the potatoes, place 2 lbs (900g) peeled and cubed Russet potatoes in a large pot, cover with cold salted water, and boil until fork-tender, about 15-20 minutes. Drain and return to the pot for 1-2 minutes to dry.

7-Add ¼ cup (57g) unsalted butter, ½ cup (120ml) half and half, ½ teaspoon garlic powder, ½ teaspoon salt, and ¼ teaspoon black pepper to the potatoes. Mash until smooth, then stir in ½ cup (50g) grated Parmesan cheese.

8-Spread the meat mixture evenly in a 9×13 inch baking dish. Top with the mashed potatoes, smoothing it out to cover everything.

9-Bake uncovered for 25-30 minutes until golden brown and bubbling. Let it cool for at least 15 minutes before serving.