Mackerel Fillets Baked in Foil Envelopes

• 4 large mackerel fillets
• 4 teaspoons butter
• Juice of 1

Butter four rectangles of tin foil and place a fillet on each one. Brush each fillet with lime juice and sprinkle with salt and pepper. Place a bay leaf, sprig of parsley and a slice of lemon on each one. Divide the capers between the four fillets, fold up the edges of the foil and anoint each fillet with 1 tablespo