Wash the mint leaves and then thoroughly pat dry; if there is any moisture the chocolate won't stick.
Using a microwave in 20 second intervals, or a bain marie, melt the chocolate until smooth. Cool slightly.
Dip a mint leaf in the chocolate, covering both sides of half the leaf (this is easiest to do by dragging the leaf through the chocolate in one direction then flipping it over and dragging back the other way). Place on greaseproof paper to set, then repeat with remaining mint leaves.