Harry Potter was a young kid who lived with his parents, James and Lily Potter. He never met any of his grandparents, but his dad had this old handwritten recipe book that was passed down from generation to generation. James' maternal grandmother gave that book to his mom, and when she died James found it among her possessions. He remembered helping his mom in the kitchen as a kid, he loved her chocolate sponge cake with salted caramel. The recipe had notes on the margin, which he knew were written by his mom.
Harry was 9 when he first found this cookbook in his dad's study. The book was opened to the recipe for a chocolate sponge cake with salted caramel. He decided to take that book and bake that cake. Young Harry has never felt that determined.
His parents were out that day, the only people with him were the house elfs, with their help Harry was actually able to make a good cake. Of course, the elfs did most of the work but Harry loved helping out. By the time his parents came back from their jobs, Harry had kept the recipe book back where it was and the cake was placed safely in the fridge.
"Mom!", Harry ran towards his parents. "Dad!"
James picked up his overly excited kid, "Hello, kiddo!"
"I made cake!", Harry told them. "Chocolate cake!"
Lily laughed it off, thinking he was joking, "Oh? I'm sure it's very tasty"
Harry grew a little concerned, "The book didn't say that I had to taste any of it."
"Which book?", James asked.
Harry knew he wasn't allowed into his dad's office, and that he wasn't allowed to touch other's things without permission.
"Your book of cakes from your desk..."
James was a little scared, "Lola."
The little house-elf popped into the room. "Hello, Master Potter."
"What happened here?"
Lola explained everything that had happened, James was happy to hear that his mom's cookbook was safe. Harry did get grounded for a week, which meant no quidditch or radio.
Soon after the dinner, Lily decided to taste test Harry's creation. She was a bit scared to try at first,
"The cake is delicious!", Lily said as she took a bite. "James, you would love it"Harry was over the moon that his mum liked the cake he kinda made, and he was more excited to see his dad's reaction.
James took a bite and he had tears in his eyes, "it's just the way she used to make it." He walked over to Harry's seat and picked him up again. "I love you, kiddo, thank you so much for this."
"Love you too, Dad.", said Harry. "It will cost you 10 galleons next time onwards."
James laughed as he kissed the top of Harry's head and let him sit again. "Of course, young man."
20 years have been passed since then, Harry was 29 years old and he had a wife and three kids. He had his own house and worked as an Auror. Harry had his grandma's recipe book now, and whenever he visits his parents, or they visit him, he bakes cakes and desserts from that book. It's potter family tradition to make a chocolate sponge cake with salted caramel every year on James' bday, and Harry never forgot to do that.