In a large stockpot over medium heat, heat the oil. Add in the shellfish shells, onions, carrots, and celery and saute for 10-15 minutes, or until lightly browned.
Add in the garlic and cook 3-4 more minutes until fragrant - you are cooking smashed whole cloves so brown the outside.
Stir in the water, clam juice, tomato paste, wine, bay leaf, thyme and parsely. Add in peppercorns then salt.
Bring to a boil, then reduce the heat and simmer for 1 hour.
Cool a small spoonful and then taste and see if you need to add more salt. Remove from the heat and strain though a mesh sieve.
Store in the fridge for 2-3 days or freeze in portions in freezer safe containers for up to 6 months.
Notes
the white wine gives this a nice bite, but as long as you use the clam juice this doesn't have to have wine in it for flavor
start with a small amount of salt, then taste-test AFTER you have boiled the shellfish shells