Preheat oven to 350 degrees F.
Grease an 8x8” square pan and set aside. (You can also line it with parchment paper for easy removal if you like)
In a small bowl, stir together sifted cocoa powder, tapioca starch and salt. Set aside.
In a microwave safe container or over the stovetop, melt butter (or coconut oil) and chocolate chips together and stir until smooth and glossy.
Add eggs, to the bowl of your standing mixer fitted with the wire whip attachment, and beat on medium-high speed for 1 minute. The eggs will be pale yellow, thicker and frothy. (You can also beat for 60 seconds with a hand-held mixer)
Add coconut sugar (or granulated sugar) to the bowl of your standing mixer and beat on medium-high speed for an additional 1 minute. The mixture will be a little thick. (You can also beat for 60 seconds with a hand-held mixer)
Add the melted butter/chocolate mixture and vanilla and beat until combined.
Add dry mixture and beat until smooth and there are no lumps.
Add ½ cup chocolate chips and stir by hand until they’re evenly distributed.
Pour batter into the prepared baking dish. Bake in your preheated oven for 18-25 minutes, or until the top is set and a toothpick inserted in the center comes out with wet crumbs!
Let sit for about 15 minutes. Serve warm or room temperature!
Store in an airtight container in the refrigerator. To return the fresh-from-the-oven taste simply reheat in the microwave for 10 seconds!