Wash and dry all produce. Preheat oven to 420 degrees. Toss carrots on a baking sheet with a drizzle of olive oil and pinch of salt and pepper. Roast until starting to brown, about 20 minutes.

Cut potatoes into 1/2-inch cubes. Place in a large pot of salted water. Bring to a boil and cook until fork tender, about 15 minutes. Drain and return to pot.

Halve, peel, and thinly slice onion. Mince garlic. Strip thyme leaves off stems. Discard stems.

Heat a drizzle of olive oil in a large pan over medium-high heat. Add beef and thyme. Cook until browned, 3-4 minutes. Remove from pan and set aside. Add another drizzle of olive oil and onions to pan. Cook until softened, about 6 minutes. Add garlic and 1/4 cup water.

Sprinkle flour over and stir 1 minute. Add stock concentrate, 1/2 cup water, and peas. Stir until sauce thickens, 2-3 minutes. Add beef and stir to combine. Use a fork or potato masher to mash potatoes with 1/4 cup milk and 1 TBSP butter until smooth. Season with salt and pepper.

If your pan isn’t ovenproof, transfer beef mixture to a medium baking dish. Spread mashed potatoes over top. Sprinkle with Parmesan cheese, and bake until melted and bubbly, about 5 minutes. Serve with roasted carrots on the side.