Heat olive oil and butter in a large stock pot over medium heat. Add the leek and sauté until tender, about 10 minutes.
Add the chopped garlic and sauté for an additional three minutes.
Gradually add the flour, whisking to prevent lumps. Cook for two minutes.
Whisk in the tomato paste.
Whisk in the bourbon and sherry. Cook for three minutes.
Add the seafood or chicken stock, heavy cream and shrimp boil. Bring to a boil, then simmer until the liquid has thickened, about 3-5 minutes. Stir frequently to prevent the cream from scorching.
Remove the pot from the heat. Add the crawfish meat and stir to combine.
Working in batches, transfer the soup to a blender and puree until smooth. Alternately, puree the soup using an immersion blender.
Return the pureed soup to the pot. Season with salt and pepper to taste.