In advance: Put 4 small glasses in the freezer, or you can serve straight into ice cream cornets, if you prefer.
When you're all set up and ready to go, get the glasses (if using) and the frozen berries out of the freezer. Divide the fresh blueberries between the glasses or cornets. Put the honey and yoghurt and leaves from the sprigs of mint into the food processor and whiz, then add the frozen berries and whiz again until combined. Spoon the frozen yoghurt over the fresh berries and serve. Yum.