1 Heat the grill to medium.
2 Line the grill tray with foil and smear with a little of the butter. Place the haddock on the buttered foil and season with a little salt and pepper, then sprinkle the fish fillets with the white wine and lemon juice and dot with the rest of the butter.
3 Place under the grill for four to five minutes until cooked.
4 Meanwhile, cook the peas in boiling water until tender – about three minutes. Drain and transfer to the pan, then add the butter and cream and roughly blitz with a blender. Top with parsley.
5 Once the fish is cooked, scatter over the parsley and top with the lemon slices. Lift the haddock fillets on to warm plates. Tip the cooking juices into a small pan, reheat if necessary, and trickle over the fish.
6 Serve with the mushy peas.