Melt the butter in a large pot over medium heat. Once the butter has melted, add the green onions and cook, stirring, until tender, about 3 minutes. Stir in the flour until fully incorporated.

Add the crawfish, shrimp, crab, cream, half and half, creamed corn, Creole seasoning, Old Bay, salt, pepper, and cayenne. Bring to a simmer over medium-high heat, stirring frequently.

Reduce the heat to medium-low and cook, stirring frequently, until thickened and the flavors have melded, about 40 minutes.

Ladle the bisque into bowls, garnish with chives, and serve with crusty bread on the side, if using.