Dice onion. Cut chicken filets into about 3 cm cubes and spice them with salt and pepper. Heat oil in a pan and fry chicken all around until filets are complete through. Lift out meat, heat butter in the pan and fry onion. Douse with wine and cook until greatly reduced. Add gravy, bring to the boil and simmer for about 2 minutes. Fold in chicken and parsley and let it sit a little bit.