Pour the oil into a 22cm frying pan. Add the onions and garlic, then cook gently for 8-10 minutes without browning.
Pat the potatoes dry with a paper towel or wrap them in a tea towel. Add to the onions, cooking slowly and turning carefully for 20-25 minutes until softened – season with salt and pepper.
Arrange the potatoes neatly in the pan, then pour the whisked eggs over them, using a fork to help them mix through.
Cook on very low heat for another 10 minutes until set.
Let the tortilla cool and rest for 20 minutes in the pan before tipping it out onto your serving dish.
Top with rocket, olives, sour cream and a sprinkle of paprika.
