Wash and dry all produce. Preheat oven to 375 degrees. Peel and slice carrot into thin coins on a diagonal. Toss carrots on a baking sheet with a drizzle of olive oil and a pinch of salt and pepper. Roast until lightly browned, about 20 minutes. Toss halfway through.

Cut potatoes into 1-inch cubes. Place in a medium pot with enough water to cover by 1 inch and a large pinch of salt. Bring to a boil and cook until easily pierced with a knife, about 15 minutes. Drain and return to pot.

Meanwhile, halve, peel, and thinly slice onion. Thinly slice mushrooms. Strip leaves off thyme and discard stems. Mince garlic.

Heat a drizzle of olive oil in a large ovenproof pan over medium-high heat. Add mushrooms and cook until golden brown, about 6 minutes. Remove from pan and set aside. In same pan, heat another drizzle of olive oil over medium heat. Add onions and season with salt and pepper. Cook until softened, about 6 minutes.

Add 1/4 cup water, garlic, peas, and thyme to pan. Cook until very soft, about another 3 minutes. Sprinkle 1/2 TBSP flour (we sent more) onto onion mixture and stir 1 minute. Add 1/2 cup water and stock concentrate. Stir until thickened, 1-2 minutes. Add mushrooms and stir to combine. TIP: If your pan is not ovenproof, transfer mixture to a baking dish.

With a fork or potato masher, mash potatoes with 1/4 cup milk (we sent more) and 1 TBSP butter. Season with salt and pepper. Spread potatoes over mushroom mixture and sprinkle with Parmesan cheese. Bake until cheese has melted and pie is bubbly, about 5 minutes. Serve with roasted carrots.