In his words: "Squamish, British Columbia. Crammed a Timbit into a strawberry vanilla and called it 'The Priestley.'" You can check out a clip of the scene here at 2:00.
After the episode aired, Tim Horton's, apparently inspired by the episode, revealed this onto their Twitter and Facebook page:
Of course, I'm pretty sure they just cut a Timbit (donut hole) and donut in half and put one inside the other for picture, but it's a cool concept regardless. I doubt they make it an actual menu item, but it's an easy do-it-yourself-er for those inclined to try.
If only I lived remotely close to a Tim Horton's though (they're mostly located in Canada and in certain states in the eastern half of the U.S.).