Rinse fish bones and trimmings thoroughly in cold water to remove blood.
Roughly chop the leeks, fennel, and carrots and place them into a large stockpot.
Chop the parsley and stems roughly and add them to the pot.
Place the cleaned fish trimmings into the stockpot with the vegetables.
Add the wine and approximately 1 liter of cold water to cover the ingredients.
Bring to a simmer over high heat and skim off any surface scum after five minutes.
Reduce heat and simmer covered for 25 minutes, skimming as needed.
Remove from heat and strain the liquid, discarding all solids.
Cool the stock and store in the fridge or freeze for later use.