Ok, it’s not really a secret how to get smooth, straight sides while icing a cake. Or if it was a secret, it’s a really badly-kept one.
So what’s my secret? It’s a dough scraper.
I do use this tool to scrape dough off my counter from time to time, but a cheap dough scraper is actually perfect for icing cakes.
Just make sure you have a nice thick layer of icing all along the sides of your cake. Use one hand to hold the dough scraper upright against the cake, and use your other hand to slowly spin the turntable. (Yes, you’ll need a turntable. I’ve tried running round the cake with the dough scraper before and you can get really dizzy.)
And that’s pretty much it. Horrible secret, ain’t it? But hey, at least your cakes will have straight sides from now on.