Pour boiling water over the peaches and leave them for 1 to 2 minutes, then pour off the water and cover them with cold water. The skins should then be easily removed. Halve the peaches, discarding stones, and place in a single layer in an ovenproof dish, cut sides up.
Mix the macaroons with the sugar and enough of the Cointreau to make a paste. Fill the peach cavities with the paste. If necessary the peach cavities can be made a little larger by removing some of the flesh, which should be finely chopped and added to the paste.
Whip in the cream and spread over the peaches. Put the peaches to chill in the refrigerator.
When ready to serve, sprinkle Demerara sugar over the cream and place under a preheated broiler until the sugar melts.