Thickly slice 500g of new potatoes and chop 1 onion.
Heat 150ml of olive oil in a frying pan. Add the potatoes and onion; cook gently, partly covered, for about 30 minutes, until soft. Stir occasionally.
Drain through a sieve, catching the oil in a bowl.
Beat 6 eggs. Fold in the potatoes, onion and 3 tablespoons of chopped parsley. Season with salt and pepper.
Heat a little reserved oil in a small 8in / 20cm non-stick frying pan over medium heat. Add the mixture and cook gently until almost set.
Cover with a large plate, carefully invert, then slide the tortilla back into the pan. Cook for a few more minutes, until set throughout. Rest for 10 minutes before slicing.
