For the mackerel, place mackerel fillets on a baking tray and lay the pickled onions over the top. Use a chef’s blow torch to cook the fish and onions. Alternatively cook under a very hot grill for 2-3 minutes.
For the gooseberry chutney, heat the olive oil in a heavy-based saucepan. Add in the onion and fry gently until softened, approximately three minutes. Then add in the ginger and sprinkle over the sugar.
Cook gently, stirring often, for two minutes. Add the gooseberries and the ginger wine or cordial. Bring to the boil, cover and simmer gently for 10-15 minutes, stirring now and then until the mixture has thickened into a chutney.
Stir in the fennel seeds and thyme leaves in the final minutes of cooking. Transfer the hot chutney into a warm, sterilised jar. Cool and seal the lid.
To serve, place the mackerel on serving plates and serve with the chutney and a few slices of baby onions. Mix the chives and crème fraîche and serve alongside.