There is a regular bus service from Mondovi to Frabosa Sottana the following link give the time table: http://www.atibus.it/Mondovi-Pratonevoso.pdf

Summarizing, your best bet should be take a fast train from Milan to Turin (if you are arriving in Malpensa airport consider that there are direct buses to Turin (at 11.30, 15.30, 20.30), you don't need to go to Milan downtown), then take a train to Mondovi where the bus to Frabosa Sottana leaves every 2 - 2.5 hours.

Ciao, Marco Milan - Italy