Heat a little olive oil in a large pan over medium heat. Add the diced potatoes and fry until golden brown and tender. Remove from the pan and set aside.
In a separate pan, cook the beef over medium heat until browned and any excess liquid has evaporated.
Add the chopped onion and peppers, and sauté until the onion becomes soft and translucent.
Stir in the diced tomatoes and cook for a few minutes until they begin to soften.
Add the tomato paste, salt, black pepper, thyme, and cumin. Mix well.
Add the sliced mushrooms and continue cooking until tender.
Transfer the fried potatoes to an oven-safe baking dish. Spoon the beef and mushroom mixture evenly over the potatoes.
Sprinkle the grated cheddar cheese over the top.
Preheat the oven to 220°C (430°F). Bake for 10–15 minutes, or until the cheese is melted, bubbly, and lightly golden.
Garnish with freshly chopped parsley, if desired. Serve hot with rice, fresh bread, or a side salad.
Notes
Store leftovers in an airtight container in the fridge for up to 3 days, or freeze for up to 2 months.