Prepare Meat Filling
Heat oil over medium-high heat. Add onions. Cook 5 minutes.
Add ground beef, parsley, rosemary, thyme, salt, and pepper. Cook 6-8 minutes until browned.
Add Worcestershire sauce and garlic. Cook 1 minute.
Stir in flour and tomato paste until incorporated.
Add broth, peas, carrots, and corn. Bring to a boil, then simmer 5 minutes.
Prepare Potato Topping
Boil potatoes until fork tender, 10-15 minutes.
Drain potatoes and return to pot. Let rest 1 minute.
Add butter, half & half, garlic powder, salt, and pepper. Mash until combined.
Stir in parmesan cheese.
Assemble and Bake
Preheat oven to 400 degrees F.
Pour meat mixture into a baking dish.
Spoon mashed potatoes on top. Spread evenly.
Bake uncovered 25-30 minutes.
Cool 15 minutes before serving.
