From Laroche-Migennes station, take the underground tunnel towards Rue Paul Bert to join the greenway for Chemilly. The route then alternates between roads and tracks between the Yonne River and the small canal to Chemilly. Careful of traffic on the outskirts of Auxerre. There are no major difficulties along this route but it requires a mountain bike.
SNCF train services
Train stations at Auxerre, Chemilly and Laroche-Migennes.
At Laroche-Migennes, a reasonable number of regional TER trains serve Paris (in c. 1hr 30 mins) and Dijon.
TER regional line Paris > Auxerre > Cravant > Clamecy > Corbigny (c. 5 trains per day). Note that few trains go further south than Cravant and check carefully on timetables before departing. Also consider the option of using a specialist private minibus shuttle service – see http://www.navette-nivernais.fr
Auxerre: mornings on Tuesdays, Fridays and Sundays