Step 1

Preheat oven to 350°F.

Step 2

Place the potatoes in a large pot of cold salted water and bring to a boil. Let cook until potatoes are very tender, about 10 minutes.

Step 3

Drain and return potatoes to hot pot. Mash with butter and milk until smooth. Stir in cheddar cheese and season to taste with salt and pepper. Cover and set aside while you work on the filling.

Step 4

In a large skillet, heat the olive oil over medium heat. Add the onions and cook until onion is soft and translucent, about 5 minutes.

Step 5

Add beef and cook until no longer pink. Add garlic and cook 1 minute more.

Step 6

Sprinkle with flour and stir frequently for 2 minutes. Gradually stir in beef broth and bring to a simmer. Cook until thickened, about 5 minutes.

Step 7

Stir in Worcestershire sauce, rosemary, thyme, carrots, and frozen peas and season to taste with salt and pepper.

Step 8

Transfer beef mixture to a 2-quart casserole dish, then top with the mashed potatoes.

Step 9

If desired, use a fork to drag patterns through the mashed potatoes, then transfer to oven to bake for 30 minutes. Broil 1-2 minutes for extra browning, if desired.

Step 10

Let rest 10 minutes before serving. Enjoy!