Bring a large pan of salted boiling water to the boil. Heat 3 tbsp oil in a medium pan and fry the garlic gently until softened but not coloured. Increase the heat, add the clams and samphire, pour over the wine and cover tightly with a lid. Cook for just 2-3 minutes, shaking the pan every now and then until the clams open
Remove from the heat and, using a slotted spoon, lift the clams and samphire out into a bowl. Return the pan to the heat and simmer until the liquid has reduced by half
Meanwhile, add the spaghetti to the boiling water and cook for 8-10 minutes or until only just tender, stirring occasionally, then drain. Remove half the clams from their shells, leaving the meat with the unshelled clams
Drop the butter into the reduced clam and wine juice and stir until it thickens. Return the clams and samphire to the liquid, then add the spaghetti and chopped parsley. Season with black pepper and toss.
