Do not let players use some homebrew they find online. It's almost always overpowered garbage.

I'd recommend that you talk to the player about what exactly is the fantasy they are looking for.

The D&D classes are primarily packages of mechanics for what a character does inside of combat. One does not cook during combat. Realistically, being a cook is more about how you roleplay outside of combat. They can pick whatever class they want, as long as they support the cook fantasy with their other choices.

You could maybe work with the player to come up with a custom background and have them use the "Chef" feat from Tasha's Cauldron of Everything as the background bonus, which is only mechanical support you will find for being a cook in 5e.

If your player wants to be Senshi from Delicious in Dungeon, they are going to have a bad time. There are simply no mechanics to support that much cooking. Nutrition isn't modelled in D&D, there isn't a monster harvesting system, every table I've ever played at forgets to even mark off rations during rests. You could homebrew a whole new mechanic for food, but this would be a big effort and may be hard to balance in a way that's fun for everyone at the table.

Don't be afraid to tell the player "no" if you don't think D&D is the right game to achieve the fantasy they want. It's better to rip that Band-Aid off quickly rather than have the game system do it over several sessions.