Soused Mackerel

Fillet and pin bone two mackerel. Set aside. In a shallow dish sufficient to take a pair of fillets side by side, strew bottom with two bay leaves, 12 white peppercorns crushed, 5 juniper berries quartered and one onion thinly shaved on a mandolin. Arrange opposing fillets on top and scatter some English mustard power over them. Strew to cover with another shaved onion. In one to two proportions sprinkle about dessert spoon of white wine vinegar followed by olive oil. Cover dish with one large tomato in 5mm slices then sprinkle with coarse breadcrumbs. Cover with well buttered greaseproof paper and put into a hot oven 180C for just under half hour. Take off greaseproof and put dish under grill until golden. Delicious