Larsen's Fish Market Seafood Chowder

6 tablespoons butter 1 large Spanish onion, diced 2 stalks celery, diced 1/8 cup mirin (sweetened sake) 1 tablespoon crab boil seasoning (recommended: Old Bay) Freshly ground black pepper 2 quarts fish stock 2 quarts clam broth 4 large potatoes, peeled and diced into 1/2-inch cubes 1/2 pound crab meat, picked over for shells 1/2 pound lobster meat, cut into bite-sized pieces 1 pound sea scallops 1 pound small shrimp, peeled and de-veined 1 pound skinned whitefish, such as cod or halibut, cut into 2-inch pieces 1 pound firm whitefish such as monkfish or swordfish, cut into bite-sized pieces 1 pint half-and-half or cream, heated (do not boil) Salt