Boil the potatoes in their skins. Cool slightly, then peel. Refrigerate for several hours or, for best results, overnight.
Soak the raisins in a small bowl of hot water for 5 minutes. Drain and pat dry with paper towels.
Very finely grate the boiled potatoes. Mix the quark, flour, sugar, eggs, lemon zest, salt, and nutmeg and knead into a smooth dough. Add the raisins and shape into a 2-inch-diameter log with moistened hands. Cut the log into 12 to 15 equal thick slices and form little patties about ¾ inch thick.
Heat the oil in a large skillet. Saute the fritters until golden brown on one side; then carefully turn them with a spatula and brown the other side. Serve warm with cinnamon sugar and some fruit compote.