Beat the sugar and butter together for several minutes until light and fluffy (I used my stand mixer).
Add the vanilla extract and beat quickly again.
Add the flour and continue to work until the mixture pulls together as a sticky dough.
Roll the dough into a rough, thick sausage shape, cover with cling-film and pop in the fridge for an hour or so.
Pre-heat the oven to 175ºC (350ºF) and line a large baking tray with greaseproof paper.
Remove from the fridge and cut into two parts (it’s easier to roll when a little smaller).
With both parts of the dough still in rough sausage shapes, start to roll each one with the palms of your hands until it starts to lengthen and smooth out a little, and you are left with a thick roll.
Cut each roll into six slices, each with a thickness of around 1.5cm (½ inch), ending up with 12 cookies. These are large but if you wanted to make them smaller just work the dough roll until it is longer and thinner.
Place the cookies on the tray and gently push around four blueberries into the tops (if they are smaller cookies you will use fewer blueberries).
Bake for around 18-20 minutes until the edges are just turning golden brown (the rest of the cookies will be pale).
Remove from the oven, sprinkle with a little sugar and leave to cool completely before moving them from the tray. Enjoy!