How to Make It
In a very large soup pot, heat 1/4 cup of the olive oil until shimmering. Add the chopped garlic, jalapeños, bell peppers, onion and bay leaf and cook, stirring occasionally, over moderately high heat until softened and beginning to brown, about 10 minutes. Add the tomato paste and cook, stirring, for 1 minute. Add the wine and cook until nearly evaporated, about 1 minute longer. Add the chopped tomatoes and their juices and cook over moderately high heat until slightly thickened, about 5 minutes. Add the clam broth and water, season lightly with salt and generously with pepper, and bring to a boil. Simmer over moderate heat until the broth is reduced to about 8 cups, about 20 minutes.
Meanwhile, in a mini food processor, combine the basil leaves with the whole garlic and process until the garlic is finely chopped. Add the remaining 1/2 cup of olive oil and the crushed red pepper and process the basil puree until smooth. Season with salt and pepper.
Working over the sink, pull off the flap on the undersides of the crabs. Remove the top shells and discard. Pry out the brownish insides and pull off the feathery lungs and discard. Rinse the crab bodies in cold water and quarter them so that each piece has body and leg.
Add the crabs and clams to the pot. Cover and cook over high heat, stirring occasionally, until the clams begin to open, about 5 minutes. Using tongs, transfer the crabs to a large platter. Add the fish, shrimp, mussels and scallops to the pot, pushing them into the broth. Return the crabs to the pot, cover and cook, stirring occasionally, until the clams and mussels are fully open and the fish, shrimp and scallops are cooked through, about 8 minutes longer.
Ladle the cioppino into deep bowls and drizzle each serving with some of the basil puree. Serve with crusty bread and pass the remaining basil puree separately.
Have the fishmonger steam the crabs for you.