Preparation Combine 2/3 cup water and 2/3 cup sugar in small saucepan. Bring to boil, stirring until sugar dissolves. Boil 1 minute. Cool syrup. Stir in lemon juice. Puree green grapes and half of lemon syrup in blender (some bits of grape peel will remain). Transfer to 13x9x2-inch metal pan. Puree red grapes and remaining lemon syrup in blender. Transfer to another 13x9x2-inch metal pan. Freeze 1 hour. Stir with fork every hour until frozen, about 4 hours. Meanwhile, dip grape clusters into 2 tablespoons Muscat wine to moisten, then dip grapes into sugar to coat. Place grapes on small tray and freeze until frozen, about 4 hours. (Granitas and grapes can be made 1 day ahead. Cover separately and keep frozen.) Using fork, scrape granitas down length of pan, forming icy flakes. Pour 2 tablespoons Muscat wine into each of 6 wide glasses. Divide green grape granita equally among glasses. Spoon red grape granita alongside green grape granita in each glass. Garnish each with sugared grape cluster and serve.
Preparation Combine 2/3 cup water and 2/3 cup sugar in small saucepan. Bring to boil, stirring until sugar dissolves. Boil 1 minute. Cool syrup. Stir in lemon juice. Puree green grapes and half of lemon syrup in blender (some bits of grape peel will remain). Transfer to 13x9x2-inch metal pan. Puree red grapes and remaining lemon syrup in blender. Transfer to another 13x9x2-inch metal pan. Freeze 1 hour. Stir with fork every hour until frozen, about 4 hours. Meanwhile, dip grape clusters into 2 tablespoons Muscat wine to moisten, then dip grapes into sugar to coat. Place grapes on small tray and freeze until frozen, about 4 hours. (Granitas and grapes can be made 1 day ahead. Cover separately and keep frozen.) Using fork, scrape granitas down length of pan, forming icy flakes. Pour 2 tablespoons Muscat wine into each of 6 wide glasses. Divide green grape granita equally among glasses. Spoon red grape granita alongside green grape granita in each glass. Garnish each with sugared grape cluster and serve.