A massive favourite of mine and the extra few minutes it takes to make will make such a difference to your finished cake and its filling. When adding a lemon, lime or passionfruit cake filling I often make a lovely zingy fresh quick curd. The curd can be used on its own but I prefer it whisked into fresh cream for a swiss roll or to top off a trifle, whisked into my cooked buttercream to make the smoothest, gorgeous less sweet filling or added to an Italian meringue or swiss meringue buttercream. The method is simple, everything goes into the pan together. The curd must be allowed to cool before using.