The 40-year-old model appeared in the final episode of the 2020 celebrity series of the Channel 4 baking show, along with reality TV judge Rob Rinder, 41, former Countdown presenter Carol Vorderman, 59, and stand-up comedian Mo Gilligan, 32.
Brook chose to model her Signature Challenge biscuits on egg muffins synonymous with fast food restaurant McDonalds, which she admitted are her favourite thing to eat for breakfast.
The biscuits were filled with chocolate to represent the burger, yellow fondant icing for the cheese slice and white butter cream topped with half a tinned apricot for the fried egg.
Judge Prue Leith said: “Do you know I think it’s really ingenious!”
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Paul Hollywood agreed: “They do look very good. Kelly do you know what I am really impressed with that. It crumbles really well and the balance of the flavours with the chocolate and the apricot. Thank you Kelly.”
He then offered her a Hollywood handshake.
Brook exclaimed: “No way! Can you believe that. Literally - I’m speechless.”
Brook later welled up with tears as she admitted she was taking part in the charity show having lost her own father to cancer.
She said: “I lost my dad in 2007 to cancer. It’s just a devastating disease that really impacted my family. I get quite emotional talking about it.
“As much as we have fun today I really am here to help anyone out there who’s been through it or will go through it.”
The model faced little competition on the baking front from the other celebrities.
Welsh TV presenter Vorderman’s Welsh cake inspired rugby shaped offerings being ruled “not a biscut” by the judges.
Judge Rinder made biscuits to look like smoked salmon bagels, but admitted he was struggling as, “I don’t eat biscuits. Or do sugar very much.”
Hollywood said they tasted quite nice, but claimed: “It’s an accident. You have burnt them. They taste nice, but look hideous.”
And comedian Gilligan, who made his own apple jam and then put his bake in the oven at the very last minute, only managed to produce two out of the required 20 biscuits onto the plate.
The celebrity spin-off of the hit baking show in aid of Stand Up To Cancer this year saw stars including Jaws star Richard Dreyfuss, documentary maker Louis Theroux, EastEnders actress Patsy Palmer and singer James Blunt among those taking part.