We report the discovery of a 1201s orbital period binary, the third shortest-period detached binary known. Sloan Digital Sky Survey J232230.20+050942.06 contains two He-core white dwarfs orbiting with a 27{deg} inclination. Located 0.76kpc from the Sun, the binary has an estimated Laser Interferometer Space Antenna (LISA) 4yr signal-to-noise ratio of 40. J2322+0509 is the first He+He white dwarf LISA verification binary, a source class that is predicted to account for one-third of resolved LISA ultra-compact binary detections.