Put bay leaves, thyme and 1 tablespoon of lavender in a piece of cheesecloth, tie into a sachet with kitchen twine, set aside.
In a small saucepan, melt 1/2 cup of the butter and add the 2 tablespoons of remaining lavender.
Remove from heat, cool, strain and set aside.
In a heavy saucepan over low heat, saute bacon, onion, celery and leeks in 1/4 cup of the remaining butter. Add garlic and wine, bring to boil and cook, uncovered until wine is reduced by 3/4. Add fish stock and the sachet, reduce heat and simmer for about 20 minutes.
Make a roux by heating the remaining 1/4 cup of butter in a small skillet over medium-high heat, vigorously whisk the flour into the butter. When the mixture thins and starts to come to a boil, reduce heat to low and whisk slowly. Stirring constantly, cook until the roux has a toasty aroma, about 2 minutes. Add roux, potatoes and parsley to the fish stock mixture. Simmer until potatoes are just tender.
Add fish and cook through, add crabmeat and cream. To serve, ladle into soup bowls and top with lavender butter and garnish with parsley.