As a child, Peeta always dreamed of having a proper, "traditional" Christmas. The Capitol didn't allow the Mellark bakery a break over the holiday season, so they would always have to continue slaving away all through Christmas. Every year though, his father would bake a small cake using the finest chocolate he could for Peeta, which would be shared between him and his brothers in secret as his mother would never approve of it.
Many years later, once Peeta had children of his own, the war had been fought and ended many years back by that point, and their new family finally had the freedom over the holiday season that Peeta had never had as a child. Freedom to have the traditional Christmas he always wanted.
After cutting down the very biggest tree they could fit into their new home, Peeta and Katniss set to work (with a laugh) helping each other bake the best damn squirrel pie that'd ever been made. For dessert, Peeta used the very same recipe his father had used every year while him and his brothers were growing up, although he baked it at least four times as big so the holiday cheer would continue on through the week (Although, their little boy had quite the endless stomach and would have attempted to eat the whole thing in one sitting had Katniss not caught him beforehand). That Christmas would forever be the very best Christmas the Mellark family had ever had, even if their son couldn't stand the taste of chocolate for the next 3 months.