Melt butter over low heat, add flour and cook 3 minutes constantly whisking. Add stock and cook and whisk until flour is absorbed, about 3 to 4 minutes. Bring to boil, return to simmer for 10 minutes. Add cream, simmer 5 minutes, again whisking constantly. Add red pepper and cheese. Cook and stir until melted. Add Champagne, oysters, green onions. Simmer 3 to 4 minutes. Cover and let stand 10 minutes. Salt and pepper, stir and serve. 12 servings