Place a rack in the center of your oven and preheat the oven to 350 degrees F. Line an 8x8-inch pan with parchment paper so that two sides overhang like handles. Lightly coat with nonstick spray.
In the bowl of a food processor fitted with a steel blade, place the avocado, eggs, coconut sugar, maple syrup, butter, and vanilla. Process until it’s completely smooth and combined, stopping to scrape down the bowl a few times as needed so that no chunks of avocado remain.
To the food processor, add the cocoa powder, almond flour, espresso powder, baking soda, and salt. Process until smooth. Add 1/4 cup chocolate chips and pulse a few times so that the chips are roughly incorporated.
Scrape the batter into the prepared pan and smooth the top. Sprinkle over the remaining 1/4 cup chocolate chips. Bake for 25 to 30 minutes, until the top is set and a toothpick inserted in the center of the brownies comes out mostly clean with just a few moist crumbs clinging to it. Place the pan on a wire cooling rack and let the brownies cool for 30 minutes. With the parchment paper handles, lift the brownies from the pan and place them on the rack to cool completely. If time allows, refrigerate for at least 4 hours or overnight. (I find that these taste their best and fudgiest the next day.) Slice and serve.
The almond flour can be swapped with hazelnut or cashew flour. It CANNOT be substituted with coconut flour, wheat-based flour, or any other flour.
Store leftovers in the refrigerator for up to 1 week, or wrap tightly and freeze in a ziptop bag for up to 4 months.