Avril Lavigne celebrated her 21st birthday with a cake-filled night out in Los Angeles on 27 September (05).

The COMPLICATED singer and her SUM 41 rocker fiance DERYCK WHILBEY, headed to Los Angeles hotspot Element to mark Lavigne's big day.

But rather than over-indulge on the alcohol she can now legally purchase and consume, the Canadian star drew great joy from the sweet treats on offer.

She says, "My favourite part of the party was the cake. I was, like, sticking my fingers in!"