Prep the pan and oven. Heat the oven to 350°F (175°C). Line an 8x8-inch pan with parchment, leaving overhang for easy lifting.

Melt the fats. In a small saucepan or microwave-safe bowl, melt the butter until just liquid. Stir in almond butter until smooth and glossy. Let it cool slightly so it doesn’t scramble the eggs.

Whisk the dry mix. In a medium bowl, whisk almond flour, cocoa powder, sweetener, baking powder, salt, and espresso powder (if using) until no lumps remain.

Beat the eggs. In a large bowl, whisk the 2 eggs, extra yolk, and vanilla until well combined and lightly frothy, about 30 seconds.

Combine. Slowly stream the warm butter–almond butter mixture into the eggs while whisking. Add the dry ingredients and stir with a spatula until just combined. Fold in chocolate chips if using. The batter will be thick.

Spread and smooth. Scrape batter into the lined pan and smooth the top with an offset spatula or the back of a spoon.

Bake. Bake 18–22 minutes, until the edges are set and a toothpick inserted in the center comes out with a few moist crumbs. Do not overbake.

Cool completely. Let brownies cool in the pan on a rack for at least 45–60 minutes. This sets the fudgy texture and helps that shiny top stay intact.

Slice and serve. Lift out using parchment and cut into 16 squares with a sharp knife, wiping the blade between cuts.