Add plummed tomatoes to a blender and blitz until they are finely chopped into small pieces. Set aside for now.
In a large pan, heat a splash of oil. Add onions and cook for 2-3 minutes or until they soften. Then add minced beef, and season with salt and pepper. Cook until the meat turns brown.
Add the blended tomatoes to the pan and bring to a boil. Add salt, pepper, Worcestershire sauce, and bay leaf, and let it cook on low heat for 10-15 minutes.
Remove your mince mix from the heat and set aside for a moment. Meanwhile, preheat your oven to 200 degrees Celsius/180 degrees Celsius Fan/Gas 6. Then, peel potatoes and cut them into similarly-sized chunks. Add them to a saucepan and cover them with water. Cook for 12-15 minutes until they are soft. Then, drain the water and add milk and butter before you mash them.
Add the minced beef to an oven dish. Cover with the mashed potatoes. Sprinkle cheese on top before placing it in the oven. Bake for 20-25 minutes or until the top is golden brown.
Notes
Serving: Let the cottage pie cool before you serve it.
Vegetables: Add your preferred choice of vegetables when making the pie.
Filling: To thicken the filling, add 1-2 tablespoon of plain flour and 2 tablespoon of water. Mix it until combined, then add to the minced beef pan.