Drizzle some olive oil into a large stockpot over a medium heat and add the fennel seeds and peppercorns
Once the seeds are sizzling, add the sliced leek, fennel, celery, onion and garlic and gently cook, ensuring you only soften and don’t colour the veg
Add the wine, turn up the heat and reduce by half
Add the fish bones to the pan. Be careful not to stir the stock too much once the bones are in, as too much agitation of the bones will turn the liquid cloudy
Top up with water until the bones are just covered, then add the kombu
Bring the stock to the boil, skim off the scum, then turn down and add the bay leaves. Simmer for 20 minutes
Turn off the heat, add the parsley stalks, herbs and lemon slices then cover with cling film and leave to infuse for a further 30 minutes
Using a ladle, scoop out the stock and pass through a sieve lined with muslin cloth into a container. Again, be gentle and try not to unsettle the bones or you’ll end up with cloudy stock
The stock will keep for 3–5 days in the fridge, or up to 3 months in the freezer
