Mix the breadcrumbs, garlic powder, paprika and salt, place in a shallow dish. Empty the flour into a shallow dish, beat the egg and nutmeg in a deep dish. Toss the mushroom slices in the flour and shake off the excess. Dip the mushrooms in the egg and then in the breadcrumbs, press firmly on the crumb coating. Heat the oil in a frying pan, fry the mushrooms in batches for approx. 2 mins. on each side, drain on kitchen paper.
Cook the potatoes in boiling salted water over a medium heat for approx. 25 mins. until soft, then drain. Heat the butter in the same pan, add the parsley and potatoes, mix, heat through gently. Plate up the nuggets and potatoes, top with the lemon wedges.