The things we did not know about the humble French-dip sandwich are, it is now clear, legion. We did not know that it was invented in Los Angeles. We did not know two restaurants dispute which of them came up with it first. And we did not know that Flatbush Farm, in Park Slope, serves what is quite possibly the best one in New York, an Haute Barnyard combination of heritage meat, melted Gruyère, and a horseradish sauce, served on name-brand bread. It's Grub Street's Sandwich of the Week, and we now know we'll be disappointed by whatever we end up scrounging for lunch.

Haute Barnyard Take on a Classic SoCal Sandwich [Grub Street]