Ms Mollard told her listeners: "She always makes the cake for her children herself.
"She loves cooking for all the family, despite the fact that they've got plenty of staff to do that for them.
"She loves making a meal for William.
"I'd love to see a picture of one of her cakes one day."
Right now, the Cambridge family is isolating together in their Norfolk home during the COVID-19 pandemic.
The Duke and Duchess of Cambridge revealed in a recent interview with the BBC in April they are in frequent contact with their parents and relatives via social media, so it is likely that Charlotte will get a special message from Prince Charles and the Duchess of Cornwall on her big day.
A royal insider also claims that Charlotte's parents have also arranged a special Zoom party to have Charlotte's friends help her celebrate, with the Queen is also expected to join.
But Charlotte isn't the only young royal who is forced to celebrate the birthday in lockdown. Prince Louis turned two on April 23, with the family marking the occasion by releasing a series of never-before-seen photos of Louis playing with rainbow paint.
One photo showed young Louis with paint on his face - adorable!
The rainbow colours also acted as a tribute to the NHS frontline workers who are helping fight the worldwide pandemic.
Adding to the celebrations, Kate and William just celebrated their ninth wedding anniversary on April 29!
The couple took to their Kensington Royal Instagram account and posted a photo from their wedding day.
In the snap, the royal pair can be seen beaming from ear-to-ear as they stood in the doorway of Westminster Abbey after exchanging vows.
"Nine years ago today – thank you for all your lovely messages on The Duke and Duchess of Cambridge’s wedding anniversary!" they captioned the photo.