Blueberry, blackcurrant and mascarpone pie

Preparation

Mix the cold butter, SteviaSweet Crystal, flour and baking powder together until it resembles breadcrumbs. Add water and knead into a smooth dough. Wrap the dough in cling film and refrigerate for 30 minutes.
 
With floured fingers, completely line a flan dish with the dough. Cover the dough with baking paper and weigh down with baking beads or, for example, rice. Bake on the middle shelf of the oven at 200 °C for around 20 minutes. Once the base has cooled a little, remove the baking beads/rice and baking paper.
 
Prepare the filling. Mix together the mascarpone, yoghurt, lemon zest and SteviaSweet Crystal. Beat the mixture using a mixer until frothy.
 
Then spread over the cooled tart base and garnish with blueberries and blackcurrants.