Caldo de pescado (Fish broth)

1 kg of thorns (usually white fish: monkfish, hake, sea bass ... )
100g carrots
100g leeks
1/2 stick of celery 
100 g of onion
black peppercorns
laurel
parsley & dill

(This is a basic spanish recipe. Fish broth will be used in other recipes)

Chop all the vegetables and fry them.  When ready grind all the vegetables in a blender or mixer. You can add some water if needed.

Enter all the ingredients in a pot with cold water. (About 1 liter, be sure all ingredients are covered) Put the heat to high. When heated, it begins to foam out. You should keep removing as it can spoil the final result. Do it few times. 

Cook for about 30 minutes, then strain and it is ready to be used or frozen.

Tips_ White wine can provide a nice taste to the fish broth. Using half liter of white wine will be enough.