Mel will join Mary in the first episode of Mary Make It Easy, a six-part series that will see the 88-year-old baker teach her celebrity friends how fun and easy it can be to whip up a delicious feast.
Mel's episode will air on November 2 at 7.30pm on BBC Two and will see the duo tackle a hearty chicken tartiflette, as well as a vegetable ragù and raspberry parfaits for dessert.
The synopsis for the episode, titled 'Weekend Wonders', reads: "Mary is joined by her dear friend of over 20 years Mel Giedroyc for a joyful camping trip. Both love spending time with their families in the great outdoors, but Mel is stuck in a rut when it comes to cooking for them, and she's relying on Mary to inspire her with some simple and delicious weekend wonders - a hearty chicken tartiflette, a speedy veg ragù and some creamy raspberry parfaits."
Mel isn't the only famous face joining Mary in the kitchen, however. Radio DJ Jordan North, Strictly star Anton du Beke, presenter AJ Odudu, singer Michael Ball and broadcaster Lorraine Kelly will all feature in half-hour episodes.
On welcoming Mel as a guest star, Mary told WhatToWatch: "We've been friends for 20 years and for this series we went camping together, which was wonderful! She wanted a few ideas for meals that she could make on camping holidays. So we made some wonderful soup and did a lovely pasta dish. But she put up the tent, which I couldn’t have dreamt of doing!"
Mel and Mary both appeared on the first seven seasons of The Great British Bake Off, with Mel hosting the show with Sue Perkins, whilst Mary was a judge alongside Paul Hollywood.
Mary, Mel and Sue all decided to depart from the show when it moved from the BBC to Channel 4.
At the time, Mary said she left the programme out of loyalty to the BBC. "It was the BBC’s program, it grew there," she told RadioTimes.com. "So I decided to stay with the BBC, with Mel and Sue."
She continued: "Well, I avoided being asked. It was suggested what would happen if I did go to Channel 4; what I would get, the advantages. But I didn’t ever have a meeting with them. I'd made up my mind. To me it’s an honor to be on the BBC. I was brought up on it."
As for why Mel and Sue stepped down from their roles, the pair said they opposed the move to Channel 4.
"The BBC nurtured the show from its infancy and helped give it its distinctive warmth and charm, growing it from an audience of 2 million to nearly 15 [million] at its peak," the pair said in a statement. "We’ve had the most amazing time on Bake Off, and have loved seeing it rise and rise like a pair of yeasted Latvian baps. We’re not going with the dough. We wish all the future bakers every success."