Heat oil in large saucepan over medium heat. Add potatoes; toss with oil and sauté about 3 minutes. Add onion and shallot; sauté for 3 minutes. Add broth and water; bring to boiling. Reduce heat; simmer, covered, 15 minutes or until potatoes are cooked through.
Transfer about 1 cup soup to blender or food processor. Whirl until pureed. Stir back into saucepan.
Add corn and pepper sauce; cook 5 to 7 minutes or until corn is tender. Add crabmeat or fish, sprigs of thyme if desired, and black pepper; simmer gently, uncovered, until crab or fish is opaque, about 5 minutes; do not boil.
Remove thyme sprigs. Add milk; gently heat through and let thicken slightly. Do not boil. Serve.