Steve Johnson, the chef at the Blue Room in Cambridge, Mass., has been cooking skirt steak for years, long before it became wildly popular. But never before has he served a better – or simpler – rendition of this long, thin band of wonderfully marbled beef. His secret: a slice of compound butter, flavored with shallots, chives and thyme, that melts over the meat. It had been so long since I had seen flavored butter on steak that this version came as something of a revelation.