According to Reader's Digest this is Gary LeVox of Rascal Flatt's Favorite Joke
John is out with his friends and stops by his grandmother's house for a visit. There's a bowl of peanuts on the coffee table, and John and his friends start snacking on them. When they're ready to leave, his friends say, "Nice to meet you, ma'am, and thank you for the peanuts." Grandma says, "You’re welcome. Ever since I lost my dentures, all I can do is suck the chocolate off of them."