Fill a large stock pot with water and bring to boil. Boil the potatoes until tender. Drain.
Transfer the potatoes to a large bowl and mash them well. Add the diced onion, olive oil, salt, pepper and lemon juice. Stir.
Fry the yellow onion in a little bit of olive oil until crispy. Set aside. Lightly fry the pine nuts until browned being careful not to burn them! Garnish the crispy onions and browned pine nuts (and fresh flat leaf parsley if desired) on top of the mashed potatoes.