From Anthony Bourdain's Kitchen Confidential:
Butter. I don’t care what they tell you they’re putting or not putting in your food at your favorite
restaurant, chances are, you’re eating a ton of butter. In a professional kitchen, it’s almost
always the first and last thing in the pan. We sauté in a mixture of butter and oil for that nice
brown, caramelized color, and we finish nearly every sauce with it (we call this monter au
beurre); that’s why my sauce tastes richer and creamier and mellower than yours, why it’s got
that nice, thick, opaque consistency. Believe me, there’s a big crock of softened butter on
almost every cook’s station, and it’s getting a heavy workout. Margarine? That’s not food. I Can’t Believe It’s Not Butter? I can. If you’re planning on using margarine in anything, you can stop reading now, because I won’t be able to help you.