1. Whisk together yolk, cream, and vanilla in small bowl; set aside. Pulse to combine 1 1/4 cups flour and sugar in bowl of food processor fitted with steel blade. Scatter butter pieces over flour mixture; pulse to cut butter into flour until mixture resembles coarse crumbs, about fifteen 1-second pulses. With machine running, add egg mixture and process until dough just comes together, about 25 seconds. Turn dough onto sheet of plastic wrap and press into 15cm disk. Wrap in plastic and refrigerate at least 2 hours.
2. Unwrap dough; lightly flour large sheet of baking paper or plastic wrap and place dough in center. roll out dough, cut out circles and line tart tins. Freeze dough 30 minutes.
3. Meanwhile, adjust one oven rack to upper-middle position and other rack to lower-middle position; heat oven to 190C. Place chilled tarts on a pre heated baking tray. Bake on lower rack 30 minutes, rotating halfway through baking time and press down any ‘Puffed” pastry. Carefully press pastry back into tins. Transfer on to upper rack and continue to bake until shells are golden brown, about 5 minutes longer.