Awwww, that's great.
I bought a kong for each of my puppies for Christmas. They like'd the idea of getting a cookie out of it, but if they couldn't do within the first minute, they just gave up and walked away (and trust me, I was making it *really* easy for them).
Then, this past weekend, I discovered the magic of peanut butter! I put a little bit of all natural organic peanut butter inside, and they kept at it for over an hour! Today I tried apple sauce and they loved that too (although it didn't take quite as long as the peanut butter).
They seem to like licking stuff out of it better than trying to make the cookie fall out.
Too bad that darn peanut butter is so hard to clean when they're done