With a mortar and pestle, crush the saffron until it creates a powder. Cover and set aside.
In a large pot over medium heat, melt 2 tablespoons of the butter.
Add in the garlic, leek, celery, and carrots. Cook until softened, about 3-5 minutes.
Add in the flour and continue to stir for about a minute.
Add in the chopped potatoes, clams, water/fish stock, crushed tomatoes, thyme, parsley, turmeric, saffron, red pepper flakes, and bay leaf. Season with salt and pepper.
Bring to a low boil. Once at a low boil, reduce heat to low. Cover the pot with a lid and cook for 30 minutes or until potatoes are softened, stirring occasionally.
Uncover and place in the fish whole. Give a light stir, still on low heat, and cook for 5-10 minutes or until the fish flakes when poked.
Stir again, breaking up the fish into pieces. Season with salt and pepper again if needed. Remove the bay leaf and serve.