Heat a large skillet; add quarter cup butter; when foam subsides, saute scallions until soft; stir in flour, coating well; whisk in stock, clam juice, wine, cream basil and seafood; stir in quarter cup cheese and set aside; saute mushrooms in the remaining butter; add garlic, cooking to aroma; combine with seafood mixture and season with salt and pepper; add pasta and mix well; pour into a buttered 9 X 13 baking dish; top with remaining cheese; bake in a preheated 190ºC oven for 15 minutes.