Prep the pan: Heat oven to 350°F (175°C). Line an 8x8-inch pan with parchment, leaving overhang for easy lifting.
Lightly grease the sides.
Mix dry ingredients: In a bowl, whisk almond flour, cocoa, sweetener, baking powder, and salt until no lumps remain.
Whisk wet ingredients: In a separate bowl, whisk melted butter, almond butter, eggs, vanilla, and espresso powder until smooth and glossy.
Combine: Stir wet into dry until just combined. Fold in sugar-free chocolate chips. Batter will be thick.
Spread and level: Scrape batter into pan and smooth the top with a spatula.
Sprinkle a pinch of flaky sea salt if using.
Bake: Bake 18–22 minutes, until edges are set and the center is slightly soft. A toothpick should come out with a few moist crumbs, not wet batter.
Cool completely: Let brownies cool in the pan on a rack for at least 30–45 minutes. For clean slices and maximum fudginess, chill 20 minutes before cutting.
Slice and serve: Lift with parchment and cut into 16 squares.
Enjoy as is or warm briefly to melt the chocolate bits.