Right now rhubarb is all over the farmers market, most of it destined for pies. And I'll be frank: this sweet and tangy base of this cocktail, made with rhubarb and some woodsy, spicy vanilla, does taste like a pie in delicious liquid form. That familiar pie flavor plays really well against two unexpected cocktail ingredients: Scottish ale and Peruvian pisco.
While it may sound like a crazy international hodgepodge, these ingredients come together into a remarkably smooth, well-integrated drink.
Why pisco? It emphasizes the light floral and citrusy flavors of the rhubarb, and offers a rich texture that gets even creamier when you add Scottish Ale. The ale is full of toasty toffee flavors that sing with the addition of vanilla scraped from the pod. Upon first taste, this cocktail may remind you of a cream soda—or something a little better than any cream soda you've ever tried.
To keep your syrup from tasting too sweet and floral, I recommend using spicier Mexican vanilla here instead of Tahitian. Tahitian vanilla can verge on perfumey, and that's just too much when you get pisco involved.