Add the quark, yoghurt, granulated sweetener and vanilla extract to a bowl and mix together well. You can add a little extra sweetener or vanilla if you prefer it a bit sweeter.
Spoon a layer of the quark mixture into the bottom of your serving dishes, then add a layer of the strawberries.
Then layer the following, quark mix > blueberries > quark mix > cornflakes > quark mix.
Finally arrange the top layer of strawberries and garnish with a sprig of mint.