Combine flour and butter with fingertips.Add coconut, sugar, baking powder and mix to combine. Add 25 ml milk and vanilla extract, bring the mixture together using hands.Add the rest of the milk 1 tsp at time just until you have a smooth dough.Form a ball, cover with cling film and rest in fridge at least 30 minutes. Roll out the dough on a flour dusted surface and cut squares about 2 inches/ 5 cm per side.
Put them on a baking tray lined with baking parchment, poke holes in them with a fork and rest in fridge for 30 minutes more.
Right before baking sprinkle them with caster sugar.
Bake at 370°F/190°C for about 15 minutes ur until gold.
Remove from oven and let them cool before touching.
They can be stored in a tin box up to a week.