This cool plant is an Echinopsis shaferi / Trichocereus shaferi that I got through eBay, maybe 10-15 years ago. The plant was supposed to flower white, but ended up having an incredibly beautiful yellow flower that had a diameter of over 20 cm AND WAS RUFFLED. Perfect flower right there. The plant is incredibly fertile and pollinates most of the flowers I put it on.
I am also aware that the Hofer family has spread some Trichocereus shaferi hybrids in the past, and I am not sure if it is one of theirs. It was supposed to be a white flowering botanical Shaferi. But who knows. This species is also VERY close to Trichocereus vollianus.