Combine the yoghurt and cinnamon in a large bowl. Pour into a shallow metal container. Place in freezer for 6 hours or until frozen.
Line a 10cm x 20cm loaf pan with plastic wrap, allowing sides to overhang. Quickly use a metal spoon to break up yoghurt. Process in a food processor until smooth. Spoon half the yoghurt into the lined pan and smooth. Cover with foil. Place in freezer. Place remaining yoghurt in a plastic container and place in freezer.
Meanwhile, to make the raspberry sorbet, combine sugar and 1 cup (250ml) water in a saucepan over low heat. Cook, stirring, for 3 mins or until sugar dissolves. Increase heat to high. Bring to the boil. Cook, without stirring, for 5 mins or until syrup thickens slightly. Remove from heat. Add the raspberries and stir to combine. Set aside to cool.
Place the raspberry mixture in a food processor and process until smooth. Strain through a fine sieve into a metal container, using a spatula to press as much pulp through as possible. Cover with foil and place in the freezer. Freeze for 6 hours or until frozen. Working quickly, use a metal spoon to transfer mixture to a food processor and process until smooth. Spoon half the sorbet over yoghurt mixture and smooth the surface. Cover with foil and place in the freezer to set. Refreeze remaining sorbet.
Repeat layers with remaining yoghurt and sorbet, allowing mixtures to soften slightly before layering. Place in freezer for 6 hours or until completely firm.
Turn onto a serving platter. Top with raspberries and mint leaves to serve.