As residential development continues to fill in the lower Broadway corridor, the area will be getting a sweet new retail addition — Tiff's Treats. The on-demand, warm-out-of-the-oven cookie delivery concept will open its third San Antonio location in the ground floor of AREA Real Estate's 1221 Broadway multifamily property. According to a construction permit, work for the $250,000 finish-out will begin in December, with the store slated for a late Spring 2016 opening. Austin-based Tiff's Treats…