Place the bones of <quantity>1</quantity> fish on a rack in a baking tray. Smoke it for 30m below <temperature>100<unit>°C</unit></temperature> until it smells and tastes smoky

Trim, peel and roughly chop <quantity>1</quantity> onion

Trim, peel and roughly chop <quantity>1</quantity> carrot

Peel and roughly chop <quantity>½</quantity> of a celeriac

Roughly chop <quantity>½</quantity> fennel bulb

Chop <quantity>1</quantity> leek

Drizzle vegetable oil in a stock pot. Add the onion and sweat it until translucent

Add the carrot

Add the remaining vegetables and mix

Let the vegetables roast

Add <quantity>¼<unit>cup</unit></quantity> of white wine

Add <quantity>1<unit>L</unit></quantity> of water and the smoked fish bones

Simmer for 6h until reduced to two thirds

Strain the fish stock and reduce it until <quantity>½</quantity>

Squeeze <quantity>2<unit>tbsp</unit></quantity> of lemon juice

Add <quantity>¼<unit>cup</unit></quantity> of butter to a pot. Cook it over medium heat until golden brown

Add <quantity>2<unit>cups</unit></quantity> of heavy cream and mix

Add <quantity>2<unit>tbsp</unit></quantity> of white wine to a heated saucepan

Add <quantity>1<unit>cup</unit></quantity> of the reduced smoked fish stock and simmer

Pour the heavy cream mixture while mixing with a hand blender

Add the lemon juice and season with salt to taste. Continue mixing until it forms a foam. The fish sauce is ready

Enjoy it!