London (CNN) -- Prince William and bride-to-be Kate Middleton's wedding may be full of all the pomp and ceremony of a traditional British state occasion, but when it comes to their wedding cake they've taken their inspiration from the United States.
Sweet-toothed Prince William has personally requested a "groom's cake" made of cookies and chocolate to be served alongside the couple's official wedding cake. The groom's cake is a wedding tradition associated with the southern United States.
Guests at the Buckingham Palace reception on April 29 will be able to choose between the "chocolate biscuit cake," as it is commonly known in the UK, and a classic fruitcake.
The groom's cake will be made by British cookie-makers McVitie's, using a secret recipe given to them by royal insiders. What is known is that huge cake will contain 17 kilos of chocolate and some 1,700 of the company's "Rich Tea" brand cookies -- enough to feed all 600 guests.
"It's going to be literally covered in chocolate decoration," Paul Courtney, the cake head chef at McVitie's said. "It's going to be beautiful."
Kate has organized the main wedding cake, commissioning luxury cake designer Fiona Cairns to make a huge multi-tiered fruit cake decorated with cream and white floral decorations.
It is a British tradition to choose fruitcake for weddings, and Cairns is famous for them. Her celebrity clients include U2 singer Bono, ex-Beatle Paul McCartney and many top London department stores.
Cairns says Kate knew exactly what she wanted: "She showed us her mood board. She had quite a few ideas and has led us as to how she would like her wedding cake to be. So, quite traditional with a modern twist really," she said.
Each tier will be made unique by delicate, handmade decorations that have been personally requested by Kate. The ornate features of Buckingham Palace will be reflected on the cake,but most of the decorations will be floral, and each has a meaning.
"I've been very much learning from her. But she has selected these flowers," said Cairns. "For example, the bridal rose symbolizes happiness, the oak and the acorn symbolize endurance ... and we have a long list. We haven't made Sweet William yet but we will."
A team of 10 has been working on the vast fruitcake, which also has to be big enough to cater for all the guests at the reception.
One royal wedding, two wedding cakes: The proof is in the eating they say and the couple will no doubt be watching to see which cake is more popular. Guesses on which cake is likely to go first ...!
Mairi Mackay contributed to this report.