From what I remember from the event about the Enma inn in fgo, she can't taste anything since her tongue was either cut (or ripped out, cant remember) from the base of her mouth and only a stub remains, meaning she shouldn't be able to talk even less cook but nevertheless she has teach every (wife wanna be) servant to cook in the throne of heroes. As to why she can cook to such an incredible degree... its literally hundreds of thousands of trail and error. Literally, thats it. She has a book where she writes down every minuscule reaction to her cooking and then simply cooks the next meal with a certain degree of variation till she arrives to something she deems worthwhile in watching people eat. So basically she's the Edison of cooking.
From what I remember from the event about the Enma inn in fgo, she can't taste anything since her tongue was either cut (or ripped out, cant remember) from the base of her mouth and only a stub remains, meaning she shouldn't be able to talk
I believe they explain her ability to talk as her using ventricolism.