Step 1Heat the oven to 275 degrees. Spread a very thin layer of the paste onto a banana leaf or sheet of aluminum foil and roast until the paste is crisp and hardened, 30 to 40 minutes. Cool, then crush before using.
Step 2Alternatively, toast the paste in a dry nonstick skillet. Spread the shrimp paste over the base of a good-quality nonstick skillet. Heat the paste over medium-low heat, scraping and stirring the paste occasionally using a firm heatproof rubber spatula. Continue to heat the paste until it is dry and crumbly, 12 to 15 minutes. Set aside to cool, then crush to a powder before using.
Step 1Place the dried chiles in a large bowl. Weight the chiles down and cover with warm water. Soak the chiles until they are softened, about 20 minutes. Drain the chiles and place them in the bowl of a food processor, along with the Thai chiles, shallots, galangal, lemongrass, turmeric, garlic and roasted shrimp paste. Puree the ingredients to form a smooth, uniform paste. If the mixture is too dry, add water as needed to help puree the paste. This makes about 2 cups of paste, which will keep, covered and refrigerated, up to 1 week.
Step 1In a medium saucepan, bring the broth and cream to a boil. Stir in the curry paste and cook until the broth is aromatic and no longer tastes raw, 3 to 5 minutes. Season the broth with oyster sauce, fish sauce, tamarind and sugar.
Step 2Add the clams and cook on a low simmer until the clams are almost cooked, about 1 minute. Stir in the basil and continue to simmer until the clams are cooked and their shells are opened (discard any clams whose shells do not open).
Step 3Taste and adjust the seasonings and flavorings if desired. Plate the curry, garnishing with the sea beans, basil flowers and thinly sliced chiles. Serve alongside steamed jasmine rice.