Ok so if you google recipes the general consensus is a ratio of 1:2:3 sugar:butter:flour i found this to taste a little flourery. I have came up with these weights and measures instead
200g granulated sugar
300g butter
450g flour
Basically cream the butter and sugar together, you can use caster sugar instead if you prefer but granulated is better. Once well creamed add the flour in 3 goes and combine until a rough dough. Do this with a wooden spoon or your hands, do not use electric mixers the idea behind shortbread dough is that it is not overworked. Once combined turn out onto a floured surface and gently either roll and cut into biscuit size portions or press into a mould/tin and pop into an oven at 160c until it just starts to turn golden and then remove and let cool. Will feel very soft to start but as cools will firm up somewhat, and you should be left with a soft smooth crumbly shortbread. Hopefully this helps !