This was a Harry Potter fan fiction in which Sirius rescues Harry when he is a kid, walks to his uncle's cabin, and uses a "cooking wand"?
This looks like The Promise by ZairaAlbereo. Here’s the part with the cooking wand:
But Sirius knew immediately what it was, and had to stifle a laugh. It was a cooking wand! He had seen James mother using it often enough, but he'd never guessed his uncle would own such a thing. In his opinion, it had always been for old little ladies really. Or for squibs, as his mother would have scoffed, although that was rubbish, since you needed to be a wizard to use one as well. But his uncle had been a rather gruff old man, who was out in the woods most of the time hunting or fishing or what not. And he had a cooking wand. Sirius snorted.