Put just enough fruit into a small ramekin to come half-way up the pot. If using grapes, halve and seed them. Cut any other fruit into small slices. Cover the fruit with the yogurt and sprinkle the sugar on top.
Place the pots under a very hot broiler (grill) until the sugar begins to bubble. Refrigerate until required.
This is a good last minute dessert for unexpected guests. If you are short of time put the pots into the freezer for 10 minutes after cooking.