Heat oven to 180C/160C fan/gas 4. Heat a pan with some olive oil, then gently fry the vegetables. Add the spices (including the garlic infused oil) and fry for a few minutes.
Tip the tomatoes into the pan, then stir in the mince, breaking it up with a wooden spoon. Add the stock and add a little less than a can of water.
Season, then part-cover and simmer for 40 mins, stirring occasionally. If there is still a lot of liquid after 30 mins, remove the lid completely and allow it to reduce a little until thickened.
Meanwhile, boil the potatoes until tender, then drain and mash with the lactose free butter and seasoning. Spoon the mince into an ovenproof dish and top with the potato, smoothing to cover the meat completely.
Mix the cheese with the tortillas, then scatter on top of the pie and bake for 10 mins to melt the cheese – take care that the tortillas don’t burn.