Need to know: Save 73% on a half-day cupcake decorating course; Learn sugar craft and cake decorating tips and tricks, including swirl piping in buttercream and how to make marshallow flowers; Take twelve of your creations home with you; Treat your mum on Mothers Day or give someone the perfect gift for Easter; What & why: If you’ve ever watched Nigella work her magic in the kitchen and thought that you could do better, here’s your chance to prove it! Today’s sweet kgbdeal has a delightful 73%…