1. In a blender or food processor, combine the tomatillos with 1/2 cup of the cilantro, the crème fraîche and lime juice and puree. Transfer to a small bowl and season with salt and pepper.
2. In a medium skillet, heat 1/2 inch of vegetable oil until shimmering. Add the tortilla strips in several batches and fry over moderately high heat, stirring occasionally, until lightly golden, about 2 minutes per batch. Using a slotted spoon, transfer the tortilla strips to a plate lined with paper towels. Sprinkle with salt.
3. Melt the butter in a stockpot. When the foam subsides, add the bacon and cook over moderate heat until crisp, about 8 minutes. Using tongs, transfer the bacon to a plate lined with paper towels and reserve for another use.
4. Add the onion, garlic, jalapeño and scallion whites to the pot and cook over moderate heat until softened but not browned, 7 to 8 minutes. Whisk in the flour, cumin and coriander and cook for 1 minute, whisking constantly. Whisk in the fish stock and bring to a boil. Reduce the heat to moderately low and simmer the soup for 15 minutes, stirring occasionally. Add the peas, scallion greens and the remaining 1/2 cup of cilantro and bring the soup to a simmer over moderate heat.
5. To serve, mound the crabmeat in the center of 12 deep soup bowls and ladle the soup over the crab. Garnish with the tomatillo crème fraîche and tortilla strips. Pass the lime wedges and hot sauce alongside.
Make Ahead: The tomatillo crème fraîche can be refrigerated overnight. The tortilla strips can be stored in an airtight container overnight. The soup can be prepared through Step 4; refrigerate overnight, but add the peas, cilantro and scallion greens just before reheating.