Preparation / Directions:
Clean the mackeral.
Zest the grapefruit, then juice it. Reserve 4 thin slices of peel.
Add an equal quantity of gin to the juice and zest. Marinade the
fish in this mixture for a couple of hours.
Remove the fish from the marinade, and grill for about 5-8 minutes
each side, depending on the size of the fish. (Until the flesh next
to the bone is just opaque.)
Meanwhile fry the onion in the butter on a low heat until just
golden. Add the marinade and sugar, and turn the heat up - simmer
the sauce until it is thickish. Adjust seasoning, and thickness
with orange juice / potato starch.