Heat a deep pot over moderate heat. Add oil and butter. As you chop your veggies, add them to the pot: potatoes, celery, onion, and red bell pepper. Add bay leaf to the pot. Season vegetables with salt and pepper and Old Bay seasoning. Saute veggies 5 minutes, then sprinkle in flour. Cook flour 2 minutes, stirring constantly. Stir in broth and combine. Stir in milk and combine. Bring soup up to a bubble. Add corn and crab meat and simmer soup 5 minutes. Adjust the soup seasonings. Remove bay leaf. Ladle soup into bread bowls or soup bowls and top with oyster crackers, hot sauce and sliced scallions.