For rum syrup: 1/2 cup sugar 1 cup water cup rum Accompaniments: vanilla custard sauce (recipe follows) sliced assorted fresh fruit such as oranges, kiwis, strawberries, and peaches Make cakes: Generously butter ten 1/2-cup individual savarin or ring molds, each measuring about 3-1/2 inches across top. In bowl of a standing electric mixer fitted with paddle attachment sprinkle yeast over milk and let stand 5 minutes. Beat in sugar, eggs, flour, and salt until combined well. Add butter, I piece at a time, beating well after each addition, and beat dough, scraping down sides of bowl, 3 minutes. (Dough will be slightly sticky.) Turn dough out onto a clean work surface and divide into 10 equal pieces. Roll each piece of dough into a rope about 8 inches long and transfer to a prepared mold, joining ends of each piece of dough to form a circle. Arrange molds on a large baking sheet and cover with plastic wrap. Let dough rise I hour. Preheat oven to 375 F. Discard plastic wrap and bake cakes in middle of oven 15 minutes, or until golden and cooked through. Make rum syrup while cakes bake: In a small saucepan combine sugar and water and boil mixture, stirring until sugar is dissolved, 2 minutes. Remove pan from heat and stir in rum. Cool cakes in molds on sheet 5 minutes. Pour about 2 tablespoons warm syrup over each cake, letting it run down sides, and let cakes stand until syrup is absorbed, about 2 minutes. Invert cakes onto a rack and brush with remaining syrup. Cool cakes completely and serve with sorbet, vanilla custard sauce, and fruit. Makes 10 savarins.