Melt the butter in a Dutch oven or large saucepan over medium heat.
Add the chopped green onion and chopped celery.
Cook until the vegetables are softened, about 5 minutes.
Sprinkle the flour over the vegetables and stir to combine.
Cook for 1 to 2 minutes to cook out the raw flour taste.
Gradually whisk in the milk, ensuring there are no lumps.
Add the freshly ground black pepper and tomato paste.
Bring the mixture to a simmer and cook for 10 minutes, stirring occasionally.
Stir in the heavy whipping cream and crab meat.
Continue to simmer for an additional 5 minutes.
Add the cooked shrimp or other seafood and sherry wine.
Simmer for a final 2 to 3 minutes, until the shrimp or seafood is heated through.
Serve hot and enjoy!