Dip glasses in water or with a lemon to moisten it. Rub the rim in sugar. This step is optional, but adds a nice touch. You could even mix some lemon zest with the sugar.
Pour one part vodka, 2 Parts limoncello in each glass. Add in well chilled Prosecco to fill the glasses about 2/4 full. Then put in a scoop of Sorbet. Garnish with lemon and mint. Drink immediately. The Sorbet will melt into the drink as you go. It's best while still at least partially frozen though, so don't let it sit for long.