In a bowl, add the oats and season with salt and pepper. Stir in the chopped parsley.
Place each fish fillet in the bowl of beaten egg and then coat in the oatmeal.
Add the butter and oil to a frying pan. When the oil is hot, add your mackerel to the pan. Cook for 2-3 minutes on each side or until crisp.
Remove the fillets from the pan and drain them on paper towels. Serve with lemon wedges to squeeze juice over the fish.
Serving Suggestions: Serve warm with chips and lemon wedges or fresh salad.