Method
- Boil the potatoes — Put the potatoes and sweet potatoes into a large pot of salted water. Boil until fork-tender, about 20–25 minutes.
- Mash the topping — Drain well, then mash with the butter and milk until smooth. Season to taste and set aside.
- Sauté the base — Heat the oil in a large pan over medium heat. Add the onions, cook 5–6 minutes until soft. Add the garlic and carrots, cook 3–4 more minutes.
- Brown the beef — Add the minced beef, breaking it up, and cook until browned all over (about 10–12 minutes) — you may need to do this in batches depending on pan size.
- Simmer the filling — Stir in the tomato paste, Worcestershire sauce, beef stock, salt, and pepper. Simmer uncovered, stirring occasionally, until thickened, about 25 minutes.
- Add peas — Stir in the peas and cook 2–3 more minutes, then remove from heat.
- Assemble — Preheat oven to 200°C (400°F). Spread the beef filling in a large baking dish (or two smaller ones). Spoon the mash evenly on top, spreading to the edges, and rough up the surface with a fork.
- Bake — Sprinkle with cheddar if using. Bake 25–30 minutes until golden and bubbling at the edges.
