For the pastry
Put the flour in a heap on a work surface. Mix in the sugar and salt and make a well in the centre.
Cut the cold butter into small pieces and scatter around the well.
Break the egg into the middle, add 1-2 tbsp lukewarm water and chop all the ingredients with a knife until they resemble breadcrumbs.
Quickly combine to a dough with your hands, wrap in clingfilm and chill for about 30 minutes.
Then divide the dough into 8 portions, knead each portion briefly and use to line 8 tart tins.
Put a piece of baking parchment into each pastry case, weigh down with baking beans or dried pulses and bake in a preheated oven (180 °C with top and bottom heat) for 20-25 minutes.
Remove the dried pulses and paper.
Leave the tart cases in the tins for about 5 minutes, then take out carefully and leave to cool on a cake rack.
For the filling
Mix the yogurt with the quark, sugar, liqueur and the seeds scraped out of the vanilla pod.
Whip the cream until stiff and fold in. Wash, sort and dry the berries.
Fill the tart cases with the yogurt cream and arrange the berries on top.
Scatter with pistachios and dust with icing sugar.
Serve garnished with mint.