Preheat the oven to <temperature>180<unit>°C</unit></temperature>

Cut the fish heads in half and remove the gills from both sides

Cut the fish bones to fit evenly on a baking tray lined with parchment paper

Roast the fish bones for 25m until deep brown. Remove the baking tray from the oven

Flip the bones over

Choose the fully roasted bones and transfer them to a stock pot

Roast the larger pieces, such as the heads, for another 25m until deep brown

Add the roasted bones to the stock pot

Cover with <quantity>2<unit>l</unit></quantity> of water

Simmer over medium heat for 30m to extract the flavors and the gelatin

Remove from the heat. Let it rest for 30m until the pieces settle to the bottom

Remove the bones from the stock

Strain the stock through a fine sieve into a clean pot

Reduce the stock by ½ over medium-low heat to concentrate the flavors. Skim it regularly

Strain the stock into a bowl and let it cool. Store in the refrigerator for up to 3 days or in the freezer for up to 2 months. The fish stock is ready

Use this fish stock as base for sauces, soups, or seafood risotto!