Preheat oven to 400°F. On a baking sheet, combine grapes, plums, pears, apples, sugar and butter; toss to coat and spread out in a single layer. Bake until soft, about 15 minutes. Let cool.
Sabayon
In a large, stainless steel bowl, whisk together egg yolks and sugar. Set over a pot of simmering water (the bowl should not touch the water). Pour in wine and whisk vigorously to incorporate air until mixture has doubled in volume and is thick like whipped cream, about 10 minutes. You can use an electric mixer if it’s easier.
To Assemle
Divide fruit among 6 dessert plates. Spoon sabayon over fruit. If desired, quickly wave a blowtorch over the surface to brown the sabayon.