One idea I have is to use them in a dunkelweizen recipe that has a lot of spicy phenolic yeast character (I like WY3638 fermented in the low 60's and slightly underpitched - gives some nice cinnamon and vanilla notes to go with the typical weizen clove and banana). I'd crush the cookies and rack over them in secondary (sort of like using fruit). I have no clue how much to use, so I'd only rack over half the batch so you can then taste and blend back. With this style you don't really have to worry about cloudiness in the beer, so it should be safe to use the cookies in secondary.
Oatmeal stout (but this seems a little obvious)
Sub them in for pumpkin/spice in a pumpkin ale recipe
This is an interesting idea. Primarily because I just racked a dunkelweizen into a keg last Tuesday. The keg is sealed, but have not started chilling or force carbing it yet. Would it be okay to siphon a portion of this onto the cookies and let sit for a ferw weeks (1-2, 2-3 weeks). It didn't ferment in the lows 60's but it was high 60's (68-69 consistently) and I used your suggested WYEAST 3638. Let me know if you think this will work.
The recipe is below.
5lbs: Weyerman Dark Wheat
3 1/2 lbs. German 2 row pilsner
1 lb German Dark Munich
8 oz Weyermann Caramunich II
4 oz Belgian Special B
1oz Tettnang hops for 60 minutes
I think it will work. I find that I lose a lot of the spicy phenolics that I like with this yeast if I ferment at higher temps, but you still get a lot of nice banana/bubblegum esters. I think it would still pair nicely with the cookies.
What would be your recommendation for the length of time this sits on the cookies? It will not be presented until our October meeting which will be near the end of October.
Would you carbonate at a normal dunkelweizen level when it is bottled?