Place the fish heads, vegetables, and seasoning in your pot.
Fill with water and bring to a boil.
Let it boil on high heat for a few minutes, then bring down to medium heat.
Simmer for 60 minutes.
Strain the stock in a fine sieve.
Place in bottles or jars and keep in the fridge for a few days. Keep the rest in the freezer for up to 14 days.