I'm a little suspicious of this product called espresso powder. Espresso is almost uniquely unsuited for being powdered, since so much of what distinguishes it from regular coffee is the intense dose of aromatic compounds. These are the exact compounds that get lost during freeze drying, which is why even the best instant coffees taste relatively bland and indistinct. The marketing copy says it's more concentrated than regular instant coffee ... but how can something be more concentrated than instant coffee? The stuff is 100% concentrated.
Is it made from a much darker roast? That just reflects a misunderstanding of espresso. Coffee beans roasted black do not make espresso. They make ruined coffee beans.
I've never been sold on using coffee to enhance chocolate flavor. But I like coffee. The best way I've found to get great coffee flavor is to infuse freshly ground beans into the dairy. For donuts, I assume there's butter; you could infuse the coffee into the butter sous-vide (chefsteps has a recipe). You get all the aromatics and all the acids, but none of the bitterness (the alkaloids aren't fat-soluble). If you're infusing into milk or cream, do it in a sealable container (like a ziploc). Use 93°C milk/cream, shake it up, seal, and after 4 minutes plunge into icewater. Don't unseal until it's room-temperature or cooler. This gets all the good flavors, including the usually elusive acidity.
