"To peel peaches, bring a medium saucepan of water to a boil. Drop 1 peach at a time gently into the boiling water, leave it for 5 seconds, and retrieve it by piercing the flesh with a fork. With a paring knife, slit the skin, which will then slip off easily." "This puree can be made several hours ahead but should be stirred before spooning onto the plates. The raspberry vinegar holds the color of the peaches, add a subtle tang, and heightens the flavor of the raspberries. Pears may be substituted for the peaches and can simply be peeled without first being dipped into boiling water." Puree the peaches in a food processor or a food mill fitted with the finest disk. (There should be about 1 cup puree.) Add the raspberry vinegar and enough of the powdered sugar to balance the taste. Refrigerate until serving time. Divide the puree among 4 dessert plates, spooning it into a semicircle. Nestle a quarter of the raspberries beside each serving of puree and pass the creme fraiche separately.