You know, he just asked her to be an advisor, not necessarily a teacher.
She just teaches the potential chef teachers, those who already know the basics, and they become the first batch of teachers.
Even in a medieval setting, the basics of preparing food, heating food, and basic bakery should be prevalent. Actually, it's even post medieval , since they practically have a high society, proper building materials, sophisticated cutlery and the such. She still has time for the cafe of hers