This is the compilation volume 1 of the "Himitsu no Recipe" series that is still being serialized in Tsubomi (yuri compilation). It's been my favorite within Tsubomi for a long time, and I was certain it would get a separate release. Here it is!
It covers the same content upto Tsubomi 11, plus a newly written chapter describing Wakatsuki's first foray into the cooking club room.
I'm listing this under Tsubomi series to keep things consistent. By the way, you do realize the same author wrote "Girl Friends," right? I love her YURI manga!