Fish and Potato Pie

• 2–2½ lb / 900 g-1.10 kg potatoes, peeled
• 6–8

Boil the potatoes and garlic together until soft. Drain and mash them with salt and pepper to taste, and most of the olive oil. Use the rest of the olive oil to brush a fairly shallow ovenproof dish. While the potatoes are cooking, scrub the mussels, tug off their beards, and knock off any barnacles with the back of a knife. Discard any mussels that remain open. Rinse the mussels thoroughly and