The children, from Hope Wood Academy in Easington Colliery, helped him prepare a festive afternoon tea to feature in his book – Big Chef Little Chef – which is published in January.
“What a fabulous and emotional day,” said Matei.
“One of the most amazing cooking experiences from my life.”
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Ten years ago Matei moved to the North East from his native Romania and competed in MasterChef in 2016.
He says Big Chef Little Chef is all about “cooking for kids with kids” and it also celebrates the bond he – Big Chef - has with his son, Armin.
Armin, Little Chef, is six-years-old and was born with cystic fibrosis.
“Just like him, these kids never let their problems stop them smiling," said Matei.
"I’m so proud of putting this book together and having the opportunity to meet and work alongside such wonderful children.
"I know it’s going to make me a better person and a better dad."
More than 200 children - aged from two to 19 - attend the Academy, which caters for young people with a diverse range of special educational needs.
Deputy head teacher Vickie Gorton said learning to cook is extremely important for the pupils to both build their independence and develop their life skills.
“We’re always encouraging the pupils to try new things and that includes different types of food,” said Mrs Gorton.
“It was fantastic having Matei here and the children really enjoyed helping him.
"We are so proud that they and Hope Wood have been chosen to take part in Big Chef Little Chef.”
One of the pupils – 11-year-old Tristan – said he was going to use his new cooking skills by making Christmas biscuits at home straight after school.
“That makes it all worthwhile,” said Matei.
“I’d been thinking about this book for a while and when I saw a photograph of Armin and me walking side by side, the idea of calling it Big Chef, Little Chef came to me."
The photograph was the inspiration for the image which will feature on the book’s front cover and on the little chefs’ aprons.
“Every dad is proud of his children and Armin is so brave and happy that I wanted us to do something really special together.
"Eating healthy food is so important – and not just for children with cystic fibrosis.
"Learning about ingredients and cooking when you are very young means you have a lifetime of understanding and enjoyment of good food ahead of you.”
As well as eating well, Armin has to take dozens of tablets each day.
He has regular physiotherapy and takes part in a number of physical activities to help him keep well.
Proceeds from the book will go to The Cystic Fibrosis Trust.
Its regional community fund-raiser Gemma Williamson said: “As well as raising money the book will also help to get people to understand.
“I think it’s fantastic and really inspiring.
"The parents of children with cystic fibrosis will really love the idea, especially all the different recipes.”
The Hope Wood pupils will help launch Big Chef Little Chef on January 26 at Seven Stories - The National Centre for Children's Books – in Newcastle.
There they will meet the 15 other junior chefs who have taken part in the project.
Anybody wishing to join them at the launch of Big Chef Little Chef should e-mail [email protected]