Melt the chocolate in a bowl set over a pan of simmering water, making sure the bowl doesn’t come into contact with the water.
Arrange three mint sticks in a triangle, securing the ends in place with the dabs of melted chocolate. Repeat to make 12 triangles and leave to set on a baking sheet lined with greaseproof paper.
Place two triangles together to make a star, securing with a few dabs of melted chocolate. Chill until set and then hang on the tree.