Wash, pluck and roughly chop the parsley, chop the onion, place in a colander and season with plenty of salt. Squeeze the onion with the salt, rinse under cold water and drain. Put the parsley and onion in a bowl, season with salt, add lemon juice, stir in a dash of oil and stir again. Wash the liver (peel off the skin if you have any) and cut it into large cubes. Put the liver in a bowl, sprinkle over 2 teaspoons of sugar and stir. Put the flour and a teaspoon of salt in a plastic bag and shake well. Add the diced liver and shake everything again. Put plenty of oil in a pan and fry the liver in it, not too hot, until golden brown. If necessary, season the parsley salt depending on the taste