Begin by creaming 125g of butter and 100g of caster sugar in a large mixing bowl until the mixture is light and fluffy, about 3-4 minutes. Gradually add in 60ml of buttermilk, mixing well until combined. Sift in 270g of cake flour, 4g of baking powder, and 2ml of salt, stirring gently until a soft dough forms. Chill this dough in the refrigerator for 10-15 minutes to make it easier to roll out.

In a separate bowl, combine 150g of desiccated coconut, 2 tablespoons of cake flour, and 1 teaspoon of baking powder. In another bowl, whisk together 134g of sugar, 120ml of sweetened condensed milk, 1.5 teaspoons of vanilla extract, 60g of melted butter, and 125ml of milk until smooth. Add the coconut mixture to the wet ingredients, stirring until everything is well combined and the filling is thick and creamy.

Roll out the chilled pastry dough on a lightly floured surface to about 1/8 inch thick. Cut the pastry into rounds that will fit your tart molds or cupcake pans, gently pressing them into the molds to create the base. Spoon the coconut filling into each tart shell, filling them generously but not overflowing. Bake the Condensed Milk Coconut Tarts in a preheated oven at 320°F (160°C) for about 20 minutes or until they are golden brown on top.

Once baked, allow the tarts to cool in the pans for about 10 minutes, which will help them set and prevent cracking. Carefully remove the tarts from the molds and transfer them to a wire rack to cool completely. These beautiful Condensed Milk Coconut Tarts can be served warm, at room temperature, or chilled, making them a versatile dessert for any occasion.