Add your flour and salt to your food processor and give it a few pulses to spread it out. Or place in a bowl and mix together.
Dot over your cold, coarsley grated butter and pulse about 20 times until it resembles breadcrumbs. Or rub in with fingertips.
Add your icing (confectioner's) sugar and pulse a few times to mix in. Or stir in.
Add your egg yolk, lemon zest, vanilla extract and 2 tablespoons of your orange juice and pulse about 15 times. If the mixture is still quite dry add another tablespoon of orange juice. Once the mixture starts to clump together a little, is soft and you can easily press it together it is ready.
Tip out onto a very lightly floured surface and bring together into a ball, no need to knead it. Flatten it out until it is about an inch deep then wrap in cling film (plastic wrap) and refrigerate for at least 30 minutes, to allow the butter to set.
Using your pastry brush, coat your tartlet cases with some softened butter, making sure you get right into the groves.
Heat your oven to 180°C Fan/200°C/390°F/Gas mark 6 and place your baking tray onto the centre shelf to heat.
Roll your pastry out to a depth of 5 mm.
Cut out circles and then press them into your tartlet cases, pressing into the groves and pushing up the sides so that the pastry just comes over the edges by a few millimetres.
Prick the base with a fork and place a circle of greaseproof (parchment) paper over the base over the tartlet (the base of a large piping nozzle is usually about the right size to use as a template), add a layer of baking beans, or a few layers of rice.
Refrigerate for 20 minutes, or place in your freezer for 10 minutes.
Place onto your preheated baking tray and bake for 7-9 minutes, until the edges are just beginning to brown a little.
Remove the baking beans and the greaseproof paper (be careful the tins and beans are very hot!) and bake for another 5 minutes, until browed at the top of the sides, the base will not be fully cooked but that's fine.
Remove and leave to cool in the tartlet tins.
Once cool, tip out of the tartlet cases and set aside.