1. Peel the pears, but leave them intact. Put them in a saucepan into which they will fit fairly snugly in one layer. Add the sugar, lemon zest and bay leaves. Pour over the cider, then add enough water just to cover the pears. Bring to a simmer, cover and simmer until the pears are tender—the time this takes can vary greatly depending on the ripeness of the pears; it could be five minutes for ripe pears, or 25 for very firm ones, so keep checking them with the tip of a small, sharp knife.
2. When the pears are done, remove them from the pan with a slotted spoon and place in a dish. Turn up the heat under the liquor in the pan. Boil it down until reduced by at least half and tastes sweet and intense. Pour the reduced liquor over the pears in their dish, leave to cool completely, then chill.
3. Before serving, spoon the juice in the dish back over the chilled pears and top with a spoonful of crème fraîche, if desired.