1. Preheat the oven to 200°C, gas mark 6. Line a baking tray with baking parchment.
2. Unroll the pastry and lay it out on a lightly floured work surface. Top with a layer of chocolate spread, then the mashed banana. Sprinkle with the nuts, then roll up from the shortest side into a tight cylinder like a Swiss roll.
3. Cut into 8 even-sized slices, then lay each slice cut side down on the prepared baking tray. Bake for 18-20 minutes until puffed up and golden.
4. Meanwhile, make the smoothies in 2 batches. Place half the frozen berries into a blender with half the honey, yogurt and apple juice, and blitz until smooth and thick. Pour into 2 tall tumblers, then repeat with the remaining ingredients. Serve with the warm swirls.