As amusing as Burger Chef is and how versatile Cheezburgers are in comparison, I'm not liking how it's coming off as a bunch of 1/day abilities. It didn't work for Arcane Archer, it didn't work for Warmage with free Sudden metamagic, I'm not seeing it work for this. Also, I'm not seeing the point of applying Spell Focus to a Cheezburger, as I can only surmise it being useful if you force it down an enemy's throat, which seems counter-productive and more the realm of scrolls, wands and staves.
What I'd recommend is to give them a pool of Cookery equal to class level + casting stat modifier per day and make the various Recipes a list of choices for the individual Burger Chef to choose, with the more powerful choices having requirements of either other Recipes or a Class Level requirement. Also, since this is essentially a crafting class, having a separate pool of Burger Making points to use up for meeting the xp requirements that Brew Potion normally requires, which makes this kind of an Artificer/Cat Burgler PrC than anything else. Alternatively, since the crafting seems aimed at quickness of making and preparation, the ability to make Cheezburgers should have some time limit on 'em, as burgers ain't that good when they've gone cold and the buns have got soggy from the sauces and grease. Perhaps it should default to 30 minutes, which increases as you take levels in Burger Chef, as your burger making skills make your food remain potent longer and just as good?
Them's my 2 coppers. Take as you will.