To remove air bubbles and produce a denser brownie, firmly tap the pan on the palm of your hand or counter several times before placing it in the oven.
If you’d like an even stronger coffee flavor, increase the espresso powder to 3 tablespoons.
Brownies will keep at room temperature for up to 3 days, but they also freeze very well. Tightly cover with plastic wrap, and store in freezer up to 2 months. Eat frozen, or thaw to room temperature.