In a discussion a few years ago, I saw the phrase, "Now you have the butter and the money." This was new to me, and a little Web searching (guided in part by a guess at the author's nationality) revealed it to be a French proverb, the full version of which is On ne peut pas avoir le beurre et l'argent du beurre: "You can't have the butter and the money for the butter." It's a really nice phrase, and maybe someday I'll be able to use it.
Bonus butter idiom: Reading the blog of a German colleague, I ran across the phrase alles wieder in Butter ("everything back in butter"), which from context appeared to mean something like "everything's all right again." Some more Web searching suggests that I was basically right, and that the idiom comes from the Middle Ages: To prevent glassware transported over the Alps from breaking in transit, a clever businessman discovered that he could set the glasses in a cask, then pour hot butter over them. As the butter cooled, it held the glasses in place, thereby preventing them from rattling against each other and cracking during transport. Everything was back in butter.