Melt butter in a large frying pan over medium-high heat. Add mushrooms and onions; cook until tender, about 3 minutes. Add wine, parsley, garlic powder, salt and pepper; cook until flavours combine, about 1 minute.
Reduce heat to low; add pork chops and spoon some mushroom mixture on top. Cover; simmer until pork is slightly pink in the centre, about 20 minutes. Remove chops from pan and keep warm.
Stir sour cream into the sauce in the pan. Increase heat to medium-high; cook and stir until well blended and hot, about 3 minutes. Spoon sauce evenly over each pork chop.