Keep an eye on Union Sq. towards the beginning of October. Chef Mark Usewicz and his partners from The Independent plan to open Toast, a small plates lounge in the space formerly occupied by Rauxa and the Elephant Walk. Filling the role of chef de cuisine? Chef Petal Joseph, the former executive sous chef at Rialto. Expect inexpensive (under $10) tasting portions of menu items like fried catfish with hot peppers and charred tomatoes and braised oxtail with dumplings and spinach.