In a small microwave-safe bowl, add the butter and unsweetened chocolate pieces. Melt in the microwave at 50% power for about 30 seconds, stir, then continue to cook and stir until all chocolate is melted and smooth.

In a large bowl, add the almond butter, erythritol, cocoa powders, peanut powder, baking soda, salt, eggs, egg yolk, water, vanilla, and the melted chocolate mixture. Use an electric hand mixer to mix until ingredients are well combined. Batter will be thick and fudgy.

Dump batter into prepared baking dish. Spread and flatten into an even layer.

Bake for 15-20 minutes, or until edges are set and beginning to crack and a toothpick inserted into center comes out with a thin layer of batter (see photo in blog post). Start checking at about 15 minutes of cooking time. Brownies will be dry (and not fudgy) if they are over baked.

Let cool in the pan for about 15 minutes, then cut into 16 squares and serve. These brownies are best served fresh on the day they are baked.