Take the leaves out of the one sprig of rosemary and crush it in a mortar and pestle to release the oils. Crush well as we are not going to strain them out and you don’t want big pieces of rosemary in between sips of your mimosas.
Mix the crushed rosemary and the vanilla to the blood orange juice.
Pour a little of it into serving flutes. Top with chilled prosecco and garnish with small sprigs of rosemary and blood orange wedges. Enjoy right away!