Submerge the potatoes with water and boil until fork-tender, 10-20 minutes. Drain and mash with milk, butter, and some salt and pepper. Set aside.

Preheat oven to 400°F (200°C).

Whisk cornstarch with broth in a small bowl. Set aside.

Saute beef in a skillet over medium-high heat until browned. Transfer to a plate.

Add onions, garlic, and carrots to the skillet. Cook 7-10 minutes until soft.

Reduce heat to medium and add tomato paste. Stir and cook 1-2 minutes.

Return beef to skillet and add broth mixture, worcestershire, thyme, and some salt and pepper. Simmer 5-10 minutes until sauce thickens.

Transfer meat mixture to a small baking dish. Spoon potatoes over the meat.

Bake for 20-30 until top is golden and filling is bubbling. Let stand for 5-10 minutes before serving.