In medium saucepan, melt butter. Add onion and green pepper; cook and stir until softened, about 5 minutes. Stir in milk, chicken broth and black pepper; bring to a boil. Stir in potato flakes; cook and stir until thickened, about 1 minute. Set aside 1 tablespoon each Cheddar and Bleu cheese for later use. Stir in remaining Cheddar and Bleu cheeses; Heat until melted, about 1 minute. Just before serving, sprinkle with reserved Cheddar and Bleu cheeses. Makes about 4 1/2 cups chowder, about 4 servings.