Prep time: 20 mins | Chill time: 1 hour | Bake time: 10–12 mins
Preheat your oven to 180°C.
In the bowl of a stand mixer fitted with a paddle attachment, beat the softened butter and brown sugar together until pale and fluffy.
Mix in the egg yolk and vanilla extract until well combined.
In a separate bowl, whisk the flour, cinnamon, baking powder, and salt.
Gradually add the dry mixture to the butter mixture. Mix until it forms a firm dough. If it's too crumbly, add a teaspoon of milk.
Shape the dough into a flat disc, wrap it in clingfilm, and refrigerate for at least 1 hour. This makes the dough easier to roll thin and helps the flavors develop.
Roll the dough out on a floured surface until it is very thin (about 3mm). Use a rectangular or fluted cutter to cut in to 20-24 biscuits.
Place on a baking tray lined with parchment paper. Bake for 10–12 minutes until the edges are golden brown. They will crisp up further as they cool.
The Crunch: For extra snap, leave the biscuits in the turned-off oven with the door slightly ajar for 5 minutes after baking to "dry" them out.
