Either cutting acrosefrom Tonnerre (home of a beautiful circular lavoir at the Fosse Dionne) or starting out from the village of Chablis, follow the course of the little Serein river (a tributary of the Yonne) toward Avallon.
From Cahblis, go along the Serein river to get to Avallon.
You'll only be able to see modern pieces from the last century at the museum which is free of crowds throughout the day.