Cut the tops off the rolls and scoop out as much of the dough as you can, leaving the crust.

Heat 250ml of water in a large shallow pan and add the clams. Put a lid on the pan and allow the clams to steam for 3–4 minutes until they open. Set a colander over a bowl, drain the opened clams and reserve the cooking liquid. When the clams are cool enough to handle, remove the meat from the shells and set aside.

Cut the potatoes into 1.5cm dice and boil them for 5–10 minutes until tender, then drain and set aside.

Melt the butter in a separate large pan over a medium heat and fry the bacon, onion or shallot, leek and celery until soft. Add the plain flour and cook for a minute or so, then add the reserved clam cooking liquor and stir until thickened. Add the milk, cream, bay leaf, potatoes and cod, then bring to the boil. Turn the heat down and simmer for about 5 minutes until the cod is cooked, then add the clam meat and season with salt, pepper and nutmeg.

Spoon the chowder into the hollowed-out bread rolls or serve in bowls with sourdough on the side. Garnish the chowder with chopped parsley or chives.