Put the clams in a sink full of water for a couple of hours to purge them of the sand and grit. Place a large saucepan (that has a lid) over direct heat, then add the oil. When it’s hot, add the garlic and get it cooking. As soon as the garlic takes on a bit of colour, add the beer and the coriander stems, and season with salt and pepper.
Bring to the boil and add the clams. Stick on the lid and give the pan a good shake. When the liquid comes to the boil again, give it another shake and cook until the clams open up, roughly 5–7 minutes. Pour everything into a serving dish, including the sauce as you’ll definitely want to mop it up with some lovely baguette or toasted sourdough. Now finish with the lemon juice, chopped coriander leaves and freshly ground black pepper.