Preheat and prep. Heat your oven to 350°F (175°C).
Lightly grease a mini muffin pan or line with paper cups to prevent sticking.
Mix dry ingredients. In a medium bowl, whisk almond flour, cocoa powder, sweetener, espresso powder, baking powder, and salt until evenly combined and lump-free.
Combine wet ingredients. In a separate bowl, whisk the egg, melted butter, vanilla, and almond milk. Make sure the butter isn’t hot or it can scramble the egg.
Bring the batter together. Pour the wet mixture into the dry and stir until just combined. The batter will be thick and scoopable.
Fold in the chocolate chips if using.
Fill the pan. Spoon the batter into the mini muffin wells, filling each about three-quarters full. Smooth the tops with the back of a spoon for even baking.
Bake. Bake for 10–12 minutes, until the edges are set and a toothpick inserted in the center comes out with a few moist crumbs. Do not overbake—these are best slightly fudgy.
Cool. Let the brownie bites cool in the pan for 10 minutes, then transfer to a rack to finish cooling.
They firm up as they cool.
Optional finish. For extra espresso flair, dust the tops lightly with a mix of sweetener and espresso powder or drizzle with melted sugar-free chocolate.