Cut frozen banana(s) into chunks and put into blender. (Be sure not to let the bananas thaw beforehand. You want to serve this dessert as cold as possible.)
Add yoghurt and lime juice.
Blend till smooth.
If it seems too thick add a little milk until it is the consistency you want. (When I use Greek yoghurt, I always add a little milk to thin it down a bit.)
Taste and then add a little sugar or honey if you'd like it to be more sweet. (Be careful not to get too sweet. It's nice to have a tiny bit of tartness from the lime.)
Spoon into a pretty glass. A wine glass works great.
Serve immediately, while it's still cold.