Until that time, Mills never really considered himself a solo artist. His first recording on his own, Break Mirrors, was released with the intention of securing more session work and becoming a producer. The end result was widely acclaimed for its overall originality in writing, arranging, and producing.
His strategy worked. He co-produced Jesca Hoop's The House That Jack Built in 2011, and produced fiddler Sarah Watkins' sophomore release, Sun Midnight Sun. Mills produced, co-produced, and/or played on several tracks by several other musicians as well as contributing to compilations. His co-production and performance of "Oh Well," with Billy Gibbons and Matt Sweeney, on the tribute album Just Tell Me That You Want Me: A Tribute to Fleetwood Mac was considered by many to be the set's highlight.
Mills produced Alabama Shakes' 2015 LP Sound & Color, which wound up snagging him a Grammy nomination for Producer of the Year, Non-Classical. He also shared in the record's win for Best Alternative Album of the Year. During 2016 and 2017, he produced albums by Perfume Genius and Dawes. He returned to his solo career in 2018 with Look, an instrumental album recorded while he was learning how to play vintage guitar synthesizers.