Using your pastry brush, grease your tart tin with your extra softened butter, making sure you get into the fluted sides.
Place your flour, cinnamon, salt and icing sugar into your food processor and whizz a few times to mix in. Check that it has all mixed in evenly. If not using a food processor, mix in a large mixing bowl.
Grate your butter, or cut it into very small cubes and place it over the flour mixture in your food processor, pulse about 20 times to turn to a sand-like consistency. If not using a food processor rub the butter in with your fingertips.
Add your egg yolk, vanilla extract and milk and pulse about 10-15 times, stop when the mixture starts to form little clumps.
Lightly flour your work surface and tip the pastry mixture out, bring it together into a ball but do not knead.
Roll your pastry out into a circle measuring 30 centimetres wide. Keep flouring under the pastry at regular intervals and turning it over, to prevent it from sticking.
Drape your pastry over your rolling pin, so that it hangs over it equally on either side, and then drape it over your tin.
Gently push the pastry into the base and fluted sides of the tin. Squeeze down any excess pastry on the sides, so that the sides are a little thicker than the base.
Roll your rolling pin over the top of the tin to trim the excess (or trim using a knife) and then gently squeeze the pastry up a little so that it sticks up about half a centimetre above the edge of the tin. This way if it shrinks a little when baking it will still be the height of the sides of the tin.
Prick the base of the pastry case with a fork and then refrigerate for 20-30 minutes, preheat your oven to 160°C Fan/180°C/350°F/ Gas mark 4.
Cut a piece of foil large enough to cover the base and sides of the pastry case. The foil needs to be tucked over the edges to cover the pastry completely.
When you have fitted the foil cover it with a layer of baking beans (or you can use rice) and bake for 20 minutes.
Remove the foil and baking beans and bake for another 10 minutes by which time the pastry should be fully baked and golden.