Heat 2 tablespoons of olive oil in a large skillet. Add 1 finely chopped yellow onion and sauté for about 5 minutes until translucent.

Add 1 pound of ground beef or lamb to the skillet and cook for 7-8 minutes until browned.

Season with 1 teaspoon each of dried parsley, rosemary, thyme, and salt and pepper to taste. Stir in 2 tablespoons Worcestershire sauce and 2 minced garlic cloves. Cook for another 2-3 minutes.

Sprinkle 2 tablespoons of all-purpose flour and mix. Add 2 tablespoons of tomato paste and 1 cup of beef broth, stirring until mixed. Simmer for about 5 minutes until thickened.

Stir in 1 cup of frozen peas, 1 cup of frozen carrots, and 1 cup of frozen corn, cooking for 3-4 minutes until tender.

Peel and chop 2 pounds of russet potatoes. Cover with water in a large pot and bring to boil. Cook for around 15 minutes until fork-tender. Drain and return to pot.

Add 4 tablespoons of unsalted butter, 1/2 cup of half & half, 1/2 teaspoon of garlic powder, salt, and pepper to the potatoes. Mash until smooth.

Preheat oven to 400°F (200°C). Spread the meat filling in a 9x13 inch baking dish. Spoon the mashed potatoes on top, spreading with a spatula.

Bake for 20-25 minutes until golden brown and filling is bubbling around edges.