Review the final conclusion of the משנה ברורה ס’ שי”ח ס”ק לז and ביאור הלכה “והדחתן why it is permitted to soak or rinse an inedible salty fish in order to make it edible and not be in violation of מכה בפטיש.
https://hebrewbooks.org/pdfpager.aspx?req=60388&st=&pgnum=274
Questions:
Does Rashi understand the violation of rinsing an old salted fish with hot water is בישול or מכה בפטיש?
Bring a proof from Rashi
Can one soak an uncooked food in a כלי שני?
Can one rinse an uncooked food by pouring directly on it from a כלי ראשון?
Learn תוס’ דף לט. “כל
The Mishna gave a rule that if a food was cooked before Shabbos it is permitted to soak it in hot water of a כלי ראשון on Shabbos to reheat the food.
Is it permitted if the food originally was just soaked in a כלי ראשון and not cooked over a fire?
See Rashi on the משנה דף קמה עמ’ ב
https://hebrewbooks.org/shas.aspx?mesechta=2&daf=145b&format=pdf
Learn רמב”ם ה’ שבת פרק כב הלכה ח
https://hebrewbooks.org/pdfpager.aspx?req=14278&st=&pgnum=100