It’s also known as superfine sugar. This sugar melts and gets incorporated into things much more quickly because it’s so fine. It’s especially useful in things like meringues. You can use regular sugar as a substitute if you grind it.
These can be cut into different shaped biscuits and used as Christmas tree decorations. To do this, cut a hole in the baked biscuits while they are still hot. Leave to cool on a wire rack. When cool, thread through green and red ribbons and tie on to the Christmas tree.