Combine the vodka, water, sugar, lemon verbena, lemon juice and zest together in a liquidiser. Blitz together, then gradually add the olive oil until the mixture forms an emulsion
Transfer the sorbet mixture from the liquidiser to an ice cream maker and churn. Stop the machine three quarters of the way through the churning process and remove the sorbet, placing it in a freezable container. Mix through the egg whites and store in the freezer until ready to serve
