Preheat the oven to 375°F (190°C) and line two baking sheets with parchment paper.
In a large bowl, whisk together the all-purpose flour, tapioca flour, cocoa powder, salt, and baking powder.
Melt the 6 ounces of dark chocolate in a glass bowl over a double boiler on the stove (complete instructions are in the blog post). Alternatively, you can melt the chocolate in a glass bowl in the microwave in 30-second intervals. Allow the melted chocolate to cool slightly.
Add the cashew butter or almond butter, maple syrup, and vanilla to the melted chocolate. Whisk until completely combined and smooth.
Add the melted chocolate mixture to the flour-cocoa mixture and stir until just combined with a wooden spoon. Fold in the chocolate chips using a rubber spatula.
If the cookie dough is too sticky to scoop up, refrigerate the batter for 10- 15 minutes (but not any longer).
Use a medium cookie scoop to form 22-24 cookies. Flatten each cookie slightly with your palm. If desired, press a few extra chocolate chips onto the top of each cookie for presentation.
Bake the cookies for 9-12 minutes (see blog post above for precise times). Remove from the oven and immediately sprinkle each cookie with flaky sea salt. Allow to cool for 5-10 minutes before devouring.