Pour the vodka, dry vermouth and olive brine into a cocktail shaker with a handful of ice and shake well.
Rub the rim of a martini glass with the wedge of lemon.
Strain the contents of the cocktail shaker into the glass and add the olives.
Place large martini glasses in the freezer. Combine the sugar and lemon juice in a small bowl; whisk until the sugar dissolves.
Combine the lemon syrup and the vodka in a martini shaker. Add ice cubes. Cover and shake 8 to 10 times, then strain the mixture equally into the very cold martini glasses. Add about 1/4 cup chilled Prosecco to each glass. Garnish each martini with a lemon slice if desired, put a twig of rosemary on top before serving.
Recette de Sébastien Goldenberg.
Recipe from Sébastien Goldenberg.