Simply add the 2 ingredients to a blender and blitz! In an ordinary blender it'll take a couple of minutes. If you have a high powered one like a Vitamix it'll take less than a minute

Wait until the dust cloud has gone down before you open the lid, otherwise your kitchen will look like a smoke bomb has gone off!

This serving amount is equal to 1 cup / 200g icing/powdered/confectioners sugar and you can make a lot and keep it in a sealed container in the cupboard indefinitely

The starch is needed to thicken buttercream frosting. If you're just using the icing sugar for dusting over a cake or say some french toast, you don't NEED to add any starch at all but it won't do any harm

To make buttercream, add 75g softened butter to 175g of the powdered sugar and beat until creamed. Add a little milk again to reach the consistency you want. That'll fill or cover an 8" cake or 12 cupcakes too