Shake gin, pisco, bitters on ice, strain in vessel of choice. Drop sugar cubes in and merely crush. Add cherries and give it all a couple brisk stirs.
I used Ole Smoky Tennessee Moonshine Cherries which are cleaner than Luxardos and a good fit for this clear drink, some fresh cherries pitted are a good alternative. The pisco is pretty hard to mix generally but the Catoctin Creek Watershed Gin has a distinct flavor which works well. And finally, the crushed sugar cubes swirled with the cherries is a unique presentation and infusion of sweetness.