Remove any membrane from the pork fillet and discard. Cut into thin strips about 1x6cm/½x2½in. Season the meat with salt and pepper.
Heat a large non stick frying pan until hot, add a little oil when very hot, then add the meat. Stir fry really briskly until brown, if cooked really fast there should be no juices, but take care not to overcook. Lift out with a slotted spoon onto a plate.
Put the lactose free butter in the pan, add the paprika and stir. Add the pork and lactose free cream to the pan and heat through. Add the lemon juice and season with salt and pepper.
Garnish with the parsley and serve the mashed potato alongside.