Translation:He has always wanted to cook for me.
There can be a lot of overlap between för/till/åt.
I think that åt is supposed to imply that you are doing the person some kind of favour, or are doing something for them because they can't, or don't have time or some such. Otherwise, I think it's okay to use the others?
I read a decent post about it once on a blog called The Swedish Teacher on this website but it's down at the moment.