1teaspoonfresh thyme leaves or ½ teaspoon dried thyme
2medium carrotspeeled and diced small (about 1 cup)
1cupfrozen peas
Mashed Potato Topping
2poundsrusset or Yukon Gold potatoespeeled and cut into chunks
1/2teaspoonkosher salt
2tablespoonsunsalted butter
4tablespoonswhole milk or cream
Garnish (Optional)
Fresh thyme or parsley
Instructions
COOK POTATOES: Add the potatoes to a large pot of salted water. Bring to a boil and cook for 15 minutes, until fork-tender. Drain, return to the pot, add butter, milk, and salt, then mash until smooth. Set aside.
START FILLING: Heat 2 tablespoons olive oil in a large skillet over medium heat. Add the onion and celery and cook for 5 to 6 minutes, until softened.
BROWN BEEF: Add the ground beef and cook for 6 to 8 minutes, breaking it up, until fully browned. Spoon off excess grease if needed.
ADD FLOUR: Sprinkle the flour over the beef mixture and stir constantly for 1 minute to cook out the raw flour.
DEGLAZE: Slowly pour in the Guinness, scraping the bottom of the pan to release any browned bits. Stir until smooth.
BUILD GRAVY: Add the hot beef stock, tomato paste, salt, pepper, thyme, and carrots. Stir well and bring to a gentle simmer. Cook uncovered for 15 minutes, until thickened and the carrots are tender.
FINISH FILLING: Stir in the frozen peas and remove from heat.
ASSEMBLE: Preheat the oven to 375°F. Transfer the filling to a deep 9-inch square or 1.5 to 2-quart casserole dish. Spread the mashed potatoes evenly over the top.
BAKE: Bake for 25 to 30 minutes, until bubbling and lightly golden on top. Broil for 2 to 3 minutes if desired.
SERVE: Let rest 5 minutes. Garnish with herbs if using and serve warm.
Notes
Make-Ahead: The filling can be made 1 day ahead and refrigerated. Add mashed potatoes just before baking for best texture.Freezing: Freeze assembled but unbaked pie for up to 2 months. Thaw overnight before baking.No Alcohol Option: Replace Guinness with additional beef stock.