In a large pot set over medium heat, warm the oil and butter. Let the butter melt, then add the bay leaf and let it sizzle until fragrant, 30 to 60 seconds. Toss in the celery and onion and cook, stirring continuously, until softened, 2 to 4 minutes. Add the garlic and salt and sauté for 2 minutes longer.
Stir in the potatoes and cook, stirring, for 1 minute. Then add the pepper, curry powder, and Old Bay, if using, and cook over medium heat to take some of the rawness out of the curry powder, about 1 minute. Stir in the flour and cook, stirring, for 2 to 3 minutes.
Pour in the broth and stir to thoroughly combine everything. Then add the coconut milk and milk. Keep stirring and bring to a boil and then reduce the heat to medium, add the corn and crab and simmer until the potatoes are tender, 8 to 12 minutes. Stir in the fennel powder and adjust the seasoning to taste. Remove and discard the bay leaf.
Ladle the chowder into bowls and garnish with the chopped chives and cilantro. (Leftovers taste even better than the first time around. Although you may need to add a little extra broth as you reheat the chowder since it tends to thicken when it sits.)