Preheat the oven to 350° F.

Make the mix according to the box instructions.

Add the instant espresso powder to the batter.

Spoon into mini-muffin pans. Top with the crushed pretzels and peanuts (and the salt if using). Bake according to the box instructions. Mini-brownie bites cook much faster than a whole pan, so if they don’t recommend a specific time start with 12 minutes. I like them a little underdone so they’re soft and chewy. You may need to cook them up to 20 minutes.

Use a toothpick to test if they’re done. If you stick a toothpick in the center of the brownie and it comes out clean, it’s cooked through.