As I understand it, the subject is at first a poor student who subsists on and works at fast food while attending school to learn gourmet cooking. Then the "fast to slow food" shows that progression. Then the "slow to fast food" isn't a regression, but I'm not sure what it means. Just that it's still fine cooking but he's getting better at it so it doesn't take as long? Or maybe just a commentary that some lowbrow foods like bacon would be "cook on fried ingredients" that do get used in highbrow cooking? The last stanza is fine enough if people couldn't get the meaning from the first two, but it does risk restating the obvious without adding anything new.