In a saucepan, heat the chicken fat (or oil) and cook the onions 5 minutes, or until soft.
Stir in the liver strips, sprinkle with flour and paprika, season with salt and pepper and cook 4 minutes.
Liver should be lightly browned, but very pink inside.
Do not overcook, as it has more cooking to do.
Stir in the boiling water, lemon juice, and sugar; cook, stirring, for 5 minutes or until the sauce has thickened.