Melt the butter in a saucepan over medium heat on the stove. 

Add the celery and green onions to the saucepan, and saute until beginning to soften. 

Stir in the flour, and saute for another minute. 

Heat the milk in the microwave until warm, and pour into the saucepan. Whisk to combine completely until all lumps are gone. 

Whisk in the heavy whipping cream, tomato paste, Old Bay seasoning and salt and pepper to taste. 

Bring to a low simmer, and continue to cook until the bisque thickens. 

Stir in the shrimp and crab meat, and cook until heated through. 

Serve topped with fresh parsley for garnish.