Boil the potatoes for 10 minutes until just tender, then drain.
Heat the oil in a medium frying pan and fry the bacon for 5 minutes until tender. Add the leek and fry for 3 minutes until soft. Add the drained potatoes and fry for a further 1-2 minutes.
Beat the eggs with the seasoning and stir in the cheese, then pour this over the potatoes in the pan. Cook for 3-4 minutes, without stirring, then cover with a lid, turn the heat down low and cook gently for 5-8 minutes until the egg has set.
Slide onto a plate and leave to cool for 5 minutes before cutting into wedges. Serve hot or cold with a side salad.
To make individual frittatas, divide the potato, leek and bacon mixture between 6 greased, deep muffin tins (10x4cm/4x1 1in) and pour the egg and cheese mixture over each. Bake at Gas 4, 180°C, fan 160°C for 25 minutes. Allow to cool before turning out.
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.