Place the sliced bananas in a single layer on a baking tray and pop into the freezer overnight.
Lift the frozen banana slices out of the freezer 5 minutes before you are ready to make the ice cream so that they can soften slightly.
Add the frozen berries to the sliced banana in a food processor and blitz until smooth.
Transfer to a freezer proof container and sprinkle over the dark chocolate, stirring it a little to combine. Pop the ice cream back into the freezer for 5 minutes whilst you make the berry sauce.
In a small saucepan add the berry sauce ingredients and bring the pan to the boil. Lower the heat and simmer for 4 minutes until the sauce has thickened.
When you are ready to serve, scoop the ice cream into bowls and top with a little drizzle of the berry sauce.