Drain the rinsed clams well and place them in a saucepan (with a lid) that fits them in a single layer. Pour over cold water to just cover (about 750ml should do it), then stir in the chilli paste, the garlic and the spring onion whites.
Cover with a lid, bring to the boil, then turn down the heat and simmer gently for 2-3 mins until the clams have all opened. Turn off the heat and stir through the beansprouts and chilli. Season with salt to taste, and decant into one large or two smaller bowls. Top with the spring onion greens and a drizzle of sesame oil, and enjoy with rice and something sharp like kimchi or pickled cucumber. You’ll need soup spoons and a bowl for the empty shells.