Again, the less-fewer distinction has always walked a fine line. We like to say the rule is "fewer" if we're talking about numbers, but of course that doesn't work if you're dealing with amounts like money or weight. "The new Chevy Malibu costs $5,000 less than the comparable Honda," is fine, for example. I would never say five thousand dollars fewer, though I would also never buy a Chevy.
Now, does one recipe call for five less cups of milk than another, or five fewer? My gut says fewer, but I could go either way.