I received this in email from the folks at Anheuser-Busch:

Winter’s Bourbon Cask Ale is back for the third year and will be available next week! A fact sheet including the taste profile, ingredients, serving suggestions and food parings, is attached along with images.

For a new twist on this barrel-aged favorite, we’ve created the “Snow Drift” – Winter’s Bourbon layered with Bare Knuckle Stout. The combination of the roasted, dark malty notes of Bare Knuckle and the vanilla, hoppiness of Winter’s Bourbon Cask Ale create a great-tasting, festive mix. See image attached.

The “Snow Drift” is part of the ongoing Bare Knuckle Stout Mix-It-Up program, which features a different beer layered with Bare Knuckle Stout each month.

The fact sheet mentioned can also be found in this PDF here.

The Winter’s Bourbon is A-B’s answer to barrel-aged beers: it’s aged on bourbon oak cask staves (which sounds like barrel-aging, but since it doesn’t actually say "aged in barrels" I have my doubts) with vanilla beans. It’s one I’ll try if I get the chance.

What’s interesting is the beer cocktail slant here; I hadn’t heard of this "Mix-It-Up" program before, and I’m only currently able to find some indirect references to it. Apparently they also did a Halloween version, "Black Pumpkin," which was Bare Knuckle Stout mixed with Jack’s Pumpkin Spice Ale. I find it intriguing, though. Anyone have a primary source? I can’t seem to find one, not even on A-B’s own website.

A picture of the Snow Drift concoction is there on the left.

Update: I posted more information—clarifying issues on both the Winter’s Bourbon and the Mix-It-Up program—here.