Preheat your grill to high. Bring a large saucepan of water with 1/2 tsp salt to the boil.
Chop the potatoes into 2cm chunks (peel first if you prefer).
When your pan of water boiling, add the potatoes and cook until you can easily slip a knife through, 15-20 mins.

Meanwhile, halve, peel and chop the onion into small pieces. Heat a drizzle of oil in a large frying pan on medium-high heat.
When hot, add the beef mince and onion. Season with salt and pepper. Cook until the mince has browned, 5-6 mins, stirring occasionally. Use a spoon to break up the mince as it cooks. IMPORTANT: Wash your hands and equipment after handling raw mince.
Meanwhile, peel and grate the garlic (or use a garlic press).

Once the mince has browned, drain and discard any excess fat. Stir in the tomato puree, garlic and rosemary, then stir-fry for 1 min.
Stir in the water for the sauce (see ingredients for amount) and red wine jus paste, then bring to the boil.
Lower the heat and simmer until thickened, 5-6 mins. IMPORTANT: The mince is cooked when no longer pink in the middle.

While the mince simmers, preheat your grill to high. Grate the Cheddar.
Once the potatoes are cooked, drain in a colander and return to the pan, off the heat. Add a knob of butter and a splash of milk (if you have any) and mash until smooth.
Season with salt and pepper. Cover with a lid to keep warm.

Once the mince mixture is ready, taste and season with salt and pepper if needed, then transfer to an appropriately sized ovenproof dish.
Top with an even layer of mash and sprinkle over the Cheddar.
Grill until the cheese is bubbling and golden, 5-6 mins.

Meanwhile, wipe out the mince frying pan and pop it back on medium-high heat with a drizzle of oil.
Once hot, add the peas and stir-fry for 2-3 mins, then remove from the heat.
When everything is ready, carefully remove the cottage pie from your grill and share between your plates. Serve with the peas alongside.
Enjoy!