Place the flour, baking powder, and caster sugar in a bowl. Add the frozen cubed butter and begin working the butter with the dough cutter into the flour mixture until the butter pieces resemble small peas. Gradually add the ice-cold water and vanilla, process with a rubber spatula until the mixture comes together, and finally knead by hand gently into a dough. Flatten into approximately 1" thick disc, cover with plastic wrap, and place in the fridge for 30 minutes.
1 cup all-purpose flour, 1/4 tsp Baking Powder, 1 1/2 cup whole wheat flour, 6 ounce unsalted butter, 1 tsp vanilla extract, 1/4 cup water, 1/3 cup caster sugar