Sanji tried to grin but it came out looking more like a lopsided smirk. "O'course I c'n cook! I'm a chef! An expertise n'fine cuisine." One of the best, if you asked him, if not the best. That would be gloating, though, and he didn't need to do that. His food could speak for him.

If he ever got the chance to actually cook for the kid, which wasn't likely. Best to keep a positive face anyway.