Heat EVOO in a deep skillet with a lid or a Dutch oven over medium-high heat. Add pancetta and render, about 3 minutes. Add chili, garlic, celery, shallot, thyme, bay, salt and pepper. Stir to soften, 5-6 minutes, then add sherry and reduce by half. Add stock and tomatoes, breaking them up with a spoon or potato masher. Stir in basil and simmer to thicken and combine flavors, 8-10 minutes.
Season cod and crab with seafood seasoning, and slide fish into sauce. Cover and cook until fish is opaque, 8-10 minutes; add crab and heat through. Serve in shallow bowls with bread for mopping.