Instructions
1 Lightly spray a 10cm x 20cm loaf tin with oil and line with plastic wrap, allowing the excess to overhang the sides.
2 In a food processor, place first bananas, yoghurt and raspberries. Blitz for 2-3 minutes, until smooth and sorbet-like, occasionally scraping down sides of the processor. Spoon mixture into prepared tin, smoothing surface with the back of a spoon. Freeze for 1 hour, or until just firm.
3 Clean out the food processor and, in it, place second measure of bananas and yoghurt with cocoa. Blend until mixture is smooth. Stir through chopped chocolate. Spoon mixture on top of raspberry layer, smoothing the surface with the back of a spoon. Freeze for 1 hour, or until just firm.
4 Clean the food processor again and, in it, blitz vanilla layer ingredients, until smooth. Spoon the mixture on top of chocolate layer, smoothing surface with the back of a spoon. Freeze for 2-3 hours.
5 To serve, remove frozen slice from freezer and set aside for 5 minutes before inverting onto a serving plate. Slice, garnish with extra raspberries and serve dessert immediately.