Fish stock

2kg white fish bones and trimmings
2 leeks, rinsed well and coarsely chopped
2 onions, coarsely chopped
Half a head of celery, coarsely chopped
Half a lemon
1tsp fennel seeds
20 black peppercorns
1 bay leaf
A few thyme sprigs
Handful of parsley
Salt

2kg white fish bones and trimmings
2 leeks, rinsed well and coarsely chopped
2 onions, coarsely chopped
Half a head of celery, coarsely chopped
Half a lemon
1tsp fennel seeds
20 black peppercorns
1 bay leaf
A few thyme sprigs
Handful of parsley
Salt

Put all the ingredients into a large pan, cover with about 1.5litres of cold water and bring to the boil. Skim well and simmer gently for 20 minutes, skimming from time to time. Strain and season to taste (be careful with the salt as you might be reducing it down in a later recipe).