Chinon is a wonderful city for walking around and finding a place that looks good to you. (Lower level, not up by the fortress. Use the public elevator.) We had pizza with duck gizzards, which was great! I don't feel our choices were worth "seeking out", even though we were satisfied with them. If I can find the business cards, I'll add them to this post in an edit.
Edit: That pizza must have been La Grappa Chinonaise, 50, rue Voltaire, 37500 Chinon
I noticed Resto KE (Z), 8, rue du Commerce, but we didn't eat there.
We had a car, so it was at a highway "big-box" Brico Marche, that we bought a 220 Volt fan for our hotel windows, and an extension cord. I still have it, but for 14.5 Euros, you could throw it away if you don't have enough free luggage. Don't miss the unusually vigorous and (appropriately) aggressive Jeanne d'Arc statue in Chinon's parking lot. In US statues, she's just a hot knight.