creamed fennel sauce

Olive oil for frying
2 large onions, finely sliced
2 medium fennel bulbs, very finely sliced
150ml dry white wine
4 fresh tarragon sprigs, leaves picked and finely chopped
200ml double cream
Juice 1/2 lemon

Heat a glug of oft in a heavy-based pan (one with a lid) over a medium heat. Fry the onions and fennel for about 20 minutes until soft. Add the white wine and tarragon and reduce for 3-4 minutes until almost evaporated.

Add the cream and bubble for 6-7 minutes to reduce by three quarters and thicken. Remove from the heat and stir in the lemon juice. Put the lid on the pan and set aside while you prepare the fish