Line a baking tray with a sheet of non-stick baking paper. Place the sliced bananas on the lined baking tray in a single layer. Place in the freezer for 2 1/2 - 3 hours until frozen.
When you're ready to make the ice cream, remove the bananas from the freezer and leave to soften a little for 5 minutes.
Place the bananas, frozen cherries, lemon juice and vanilla extract in a food processor or blender and blitz for a minute or two until thick, smooth and creamy. You will need to scrape the mixture down from the side of your food processor occasionally. You may need to do this in two batches depending on the size of your food processor or blender.
Working quickly, scrape the mixture into a medium mixing bowl using a spatula. Fold in the chocolate chunks and scrape into a 1 L freezer-proof container. Roughly spread out, cover with a lid and place in the freezer for about 4 hours until frozen.
When ready to serve, remove from the freezer and leave to soften for about 10 minutes before serving.