Yuuri learned to cook from Hiroko and as such can do it pretty well. Not as good as Hiroko but I imagine he helps a lot with foodprep at Yu-Topia so if nothing else he can chop and mince and boil with the best of them. There’s also a possibly that Yuuri doesn’t think he can cook as well as his mother because the dishes always come out tasting slightly different but it’s just because he’s making it in a different place with different cookware and he’s a different person. Anybody who’s been cooking for long enough knows that there are subtle differences in a dish depending on who makes it–not for better or for worse, just different. Even if you follow the same recipe, something will always be a little different.
Also, though, also–Yuuri spent entire weeks his freshman year of college subsisting off of ramen and cheese on bread. This is before he gets any major sponsorships and he didn’t want to ask his parents for extra money for food. Celestino noticed that he wasn’t gaining enough muscle mass in training, though, and that he was getting sick quite often. When he found out he called Hiroko HIMSELF and asked if they were having trouble paying for Yuuri’s college expenses because he would help them as best he could–he would reduce his coaching fee or something, because damn.
Hiroko’s response is basically to say WAHT and ask Celestino to find her son and put him on the phone. It’s one of only three times in Yuuri’s life that his mother has really, noticeably raised her voice to him.