Lightly MUDDLE mint (just to bruise) in base of glass. Add rum, lime juice and sugar free sweetener. Half fill glass with crushed ice and CHURN (stir) with bar spoon. Fill glass with more crushed ice and CHURN some more. TOP with soda, stir and serve with environmentally friendly straws.
Adapted from the classic serve by yours truly (Simon Difford) in January 2019.