It starts about 9:30 and there is a train that gets in around 9:15 and then it is over late around 7 or 8. I see there are late trains to Florence.
IMHO there is no way you make the start of the class, even if the train is on time, even with a taxi. You need to get up the hill and then find the building. Which may be a moot point, because I don't remember taxis meeting the train although its always possible that one will be sitting there.
The bus up the hill is easy. Here is the google map pic showing the stop with the station behind. https://goo.gl/GckBeS If there is no earlier train then you're not going to make the class with the bus.
If this was me I'd take the train the nite before the class and spend 2 nites. The arrival afternoon explore town a bit (its a small town!) and have drinks at the place overlooking the valley right by car turnaround https://goo.gl/bgF5DS (that picture is on a cloudy day, on a sunny day the views are stunning!) and a nice dinner somewhere. Since the class ending time is vague and may run late, it will be hard to commit to catching a particular train that nite unless you want to leave even if the class isn't over. And to me that kind of begs the point of travel. It isn't to move efficiently from A to B to C with nary a wasted minute, nor is that possible in many cases without a lot of stress. Instead I'd prefer to enjoy the cooking experience without worries of missing a train or having in the back of my mind plans for that nite in some other location. A day spent somewhere can take 2 nites, that's just the way it works.