Use electric beaters to beat the butter in a bowl for 6 minutes or until pale and creamy, scraping down the side of the bowl with a spatula once or twice.
With the beaters running at a low speed, slowly add the condensed milk.
Bring the mixer back up to top speed and beat for 2 minutes or until well combined.
Add lemon rind, lemon curd and a few drops of yellow food colouring to the bowl.
Use electric beaters to beat for 60-90 seconds or until well combined.
Spoon into a piping bag fitted with your preferred nozzle (we used a 9mm star nozzle). Pipe as desired.