Aside from his hunter’s journal, Dean has a second notebook hidden in his nightstand: a collection of recipes he’s picked up from various places. They’re not every recipe he’s ever tried, but just the most successful ones, the ones that leave him sated and happy, stomach heavy in the good way.
He goes through a lot of recipes to fill up that notebook. Most of them he tries on himself first, sometimes with Sam and Cas as a family meal. Some he tries just with Cas (and by complete coincidence, that’s mostly food you don’t need utensils to eat, so there’s a lot more cutesy hand-feeding going on than Dean would like to admit to).
Dean doesn’t get a chance to cook as often as he’d like, but when he does he enjoys it, just as much as he enjoys eating the results. And the slight pudge he’s beginning to collect around his middle, well, he kind of enjoys that too. It’s a nice reminder of how settled he’s gotten.
(Not to mention that Cas shows a lot of appreciation for it, with his hands and his lips, and soft words when he thinks Dean can’t hear him)