Preheat oven to 180°C. Combine the flour and butter in a bowl and rub until the mixture resembles wet sand. Add the muesli and mix again, then stir in the yolk, 1 tsp vanilla and 2 Tbsp iced water until it forms a dough. Wrap and refrigerate for 1 hour.
Roll out the dough to 4mm thick, then cut out four 16cm discs and press into 10cm tartlet tins. Line with paper and baking weights then bake for 20 minutes, until crisp.
Whip the ricotta, yoghurt, icing sugar and remaining vanilla until smooth, then spoon into granola shells and top with fruit. Spoon the sauce onto plates, then top with tartlets, double cream, icing sugar and orange zest.