Who wrote the משנה ברורה?

Who wrote the משנה ברורה? The משנה ברורה שי"ח ס"ק י"ד ) writes:          " Food that was cooked for a sick person on  Shabbos, even healthy people may eat it immediately on Motzei Shabbos. (Since it was  cooked בהיתר  there is no problem of בישול עכו"ם &  no need of בכדי שיעשו) " The Dirshu Mishna Berurah quotes from the  (שביתת השבת & שונה הלכות (ר' חיים קניבסקי שליט"א who ask from the מ"ב שכ"ח ס"ק סג "Food cooked for a חולה on  Shabbos may not be eaten on Motzei  Shabbos even for the חולה, since you  can cook for him fresh food on Motzei  Shabbos." The שביתת השבת & שונה הלכות answer various answers to solve the contradiction in the מ"ב. In the ספר כל ספרי החפץ חיים ח"ג There is a chapter written by the son of the Chofetz Chaim הרב אריה לייב הכהן זצ"ל. He writes that the Chofetz Chaim paid him a monthly salary of 20 Rubles so that he will help him with writing the מ"ב. The first volume of the מ"ב and most of volume 3 was written entirely by the Chofetz Chaim.  The rest of the מ"ב R. Aryeh used to send to the Chofetz Chaim his pieces of Mishna Berurah & Biur Halacha. The Chofetz Chaim reviewed (edited) and entered them in the Sefer. When the Chofetz Chaim wasn't satisfied he rejected it and entered his own. There were times when a Halacha somehow slipped through and was entered even though the Chofetz Chaim was not in agreement with it.  Therefore you will find at times contradictions in the מ"ב.  One such example is the סתירה in the מ"ב between סימן שי"ח & סימן שכ"ח  R Aryeh writes that in שי"ח is the Psak of the Chofetz Chaim who allowed eating the food immediately after Shabbos. In  שכ"ח is his own Psak where he argues on his father and forbids food cooked by an Akum on Shabbos to be eaten after Shabbos.