Heat the olive oil in a large, heavy-based frying pan. Add the potato cubes and onions, then
lower the heat and cook, stirring frequently so that the potatoes do not clump together, for 20
minutes or until tender but not browned. Place a sieve over a large bowl and drain the potatoes and
onions well. Set aside the oil.
Beat the eggs lightly in a large bowl and season well with salt and pepper. Gently stir in the
potatoes and onions.
Wipe out the frying pan with kitchen paper and heat 2 tablespoons of the reserved olive oil.
When hot, add the egg and potato mixture, lower the heat and cook for 3-5 minutes or until the
underside is just set. Use a spatula to submerge the potatoes in the egg and loosen the tortilla
from the bottom of the frying pan to stop it sticking.
Cover the tortilla with a plate and hold the plate in place with the other hand. Drain off the
oil in the frying pan, then quickly invert the tortilla onto the plate. Return the frying pan to
the heat and add a little more oil if necessary. Slide the tortilla, cooked side uppermost, back
into the frying pan and cook for a further 3-5 minutes or until set underneath.
Slide the tortilla onto a serving plate and let stand for about 15 minutes. Serve warm or cold,
garnished with parsley sprigs.