Ted's already been pretty open about cooking being something he did for his mother when his father died. There's just a little more to it that that. His suicide really broke her, and for a while Ted felt like he was the only one holding everything together.

He could easily have hated cooking after that, bitter at having that responsibility. But no, he still loves it. He eventually learned to cook simply for fun, at that way it remained a good thing he could do for himself as well as other people, not just something he was forced into.

And it's obvious that he enjoys it too. He moves around the kitchen with a content purpose, gathering ingredients and mixing them together.