Preheat the oven to 190C/gas
5/fan 170C. Peel and thinly slice
the potatoes and put immediately
into a bowl of cold water. Using
some of the butter, liberally grease
a 20-23cm cake tin (not loosebottomed).
Drain the potato slices and dry
thoroughly in a tea towel. Place the
potato slices in circles in a layer in
the base of the tin, overlapping
them as you go. Season with salt
and freshly ground black pepper
and dot with a few small pieces of
butter. Keep layering the slices
evenly, seasoning and dotting with
butter as you go. Finish with butter,
season, then cover with a circle of
buttered greaseproof paper.
Bake for 1½ hours, or until the
potatoes are tender when pierced
with the tip of a knife.
Leave to cool in the tin for 5
minutes, then invert on to a serving
plate. Brown briefly under a hot grill
if the top needs more browning.
Serve cut into wedges.