I saw this recipe on the blog of Edd Kimber – aka The Boy Who Bakes – and had to try it.
They look very cute but are lacking the custardy punch I was hoping for. The quantities of icing sugar and butter Edd gave resulted in a gritty sandy mixture rather than a fluffy icing so I added a couple of dollops of butter to make it come together. That said, I do commend a recipe that gives an accurate quantity of filling/topping overall (my freezer contains far too many tiny tubs of leftover icing which I can’t bring myself to chuck at the time, but never get round to using).
When it did become a single mass of icing, it had a fantastic texture which I suspect is down to the custard powder. Custard powder is imbued with magical qualities that any physics geek will happily expound on, but insist on using fluid dynamics rather than magic to explain. Or maybe that’s just my resident physics geek.
This magical mixture was easily rolled into a ball and pressed to make little disc of filling, and I found this easier than trying to pipe it (didn’t have the right nozzle anyway) or spread it (the cookies are very delicate and break if you press too hard) so it might also work for you.
The recipe makes 20 sandwiched biscuits when using a 5cm round cutter.