Stir 3/4 cup sugar and 3/4 cup water in large saucepan over low heat until sugar dissolves. Cool. Puree 1 cup strawberries in processor. Whisk 1/2 cup puree into sugar syrup. Mix in grapefruit juice, then Champagne. Pour mixture into 8-inch square metal baking pan. Freeze mixture until firm, stirring every 2 hours, about 6 hours. (Can be made 2 days ahead. Cover; keep frozen.) Mix remaining 1/2 cup sugar and lemon peel in pie plate. Spread 1/2 teaspoon mascarpone around pointed tip half of each whole strawberry. Dip in lemon sugar to coat mascarpone. Moisten rims of 6 Martini glasses with water; dip rims into remaining lemon sugar. Scrape fork across surface of granita to form ice shavings. Mound granita in glasses. Garnish with sugared berries and serve immediately. *Available at Italian markets and some supermarkets.