What will tonight’s secret ingredient be? Marshmallows? A T-square? Tea squares? To help raise funds for the Urban Assembly School of Design and Construction, a charter founded in 2004 to teach and promote architecture and design, the school is hosting the Iron Designer Challenge tonight. Like an ARCH DL for a good cause, teams of four professionals and two students will compete for the title of champion, as well as structural innovation, people’s choice, and, of course, best use of the secret ingredient. Teams will start at 5:00, with three hours to finish their work, but there is also a party open to the public—this is a fundraiser, after all—from 6:00 to 8:30. Tickets are 50 dollars, but you get to mingle on the roofdeck with the likes of the jury, DDC commish David Burney, SHoP principal Gregg Pasquarelli, Cooper-Hewitt ed head Caroline Payson, and Parsons architecture dean Joel Towers. Plus, there’s a damned impressive designy silent auction.