Organise all the necessary ingredients. I recommend using a digital kitchen scale for an accurate measurement of quantities.
In a flat bottom pastry bowl, work the icing sugar and soft butter with a wooden spatula...
... until the preparation has a homogeneous consistency.
Add the egg...
... and vanilla extract, then combine until completely incorporated.
Add the flour (sifted beforehandd) and salt.
Combine again until a compact ball forms.
Finish working the dough with your hands.
Knead the dough, stretching it and regathering it, for a short while (this technique is called 'fraisage'). Refrigerate for 30 minutes before use. Due to its crumbly consistency, you may need to divide this sweet shortcrust pastry into small balls in order to line a tart tin.