Mix together the oats, yoghurt, grated apple, granulated sweetener, and vanilla extract.
Place your mixture in the bottom of a lidded 350ml jar.
Spread the blackcurrants over the top of this layer – saving a few for the top.
In a clean bowl, mix together the "custard" ingredients – yoghurt, quark, vanilla extract, chia seeds, and granulated sweetener. Beat it well to remove any lumps.
Pour this mixture over the blackcurrants, adding the saved blackcurrants on top, then close the lid of your jar, and refrigerate overnight.