Bread and Butter _____ my family's daily food 10 years ago.

(Grammar Questions I Couldn't Answer)

This question comes from one of my Vietnamese colleagues.
His student (also Vietnamese) was working through fill in the blank exercises in his grammar book, and came across this sentence:

Bread and Butter _____ my family's daily food 10 years ago.

He had to select either "was" or "were" to fit in the blank.

My native-speaker intuition was telling me either could really work here, but I was kind of leaning towards "was".  But why?

"Bread" and "Butter" were both uncountable nouns.  Uncountable nouns take the singular verb.  But in this case there were two of them, so together they made a plural subject, right?  So why was I leaning towards "was" ?

Perhaps because the predicate "food" was also uncountable?

Or perhaps my native speaker intuition was off?