Line a large tray with baking paper.
Mix the butter, sugar and vanilla extract together until smooth.
Stir in the flour until it starts to stick together. Then use your hands to press everything together into a ball of dough. If it's too wet, add more flour. If it's too dry, add a small splash of milk.
Gently knead in the cranberries.
Roll the dough onto a lightly floured surface until it's around ¼-inch thick. Use a 3-inch cookie cutter to cut out your biscuits. Re-roll scrap pieces together until all of the dough is used up.
Place the biscuit shapes onto your lined tray then pop them in the fridge for 30 minutes. This will help them to hold their shape in the oven.
Preheat your oven to 180℃(350℉) or 160℃(320℉) if you're using a fan oven.
After the 30 minutes have passed, bake your biscuits for 18-20 minutes. You'll know they're done when they're firm around the edges with a slightly soft centre. They'll become more crunchy as they cool so be careful not to overbake them.
Sprinkle some extra sugar on top of the biscuits while they're still warm. Let them cool on the tray then enjoy!