Begin by gathering all your ingredients. Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking dish by greasing it.
In a mixing bowl, combine walnuts and chocolate chips with a teaspoon of cocoa powder until they are well coated, then set them aside. In another bowl, whisk together tapioca flour, sorghum flour, teff flour, 1/3 cup of cocoa powder, xanthan gum, and a pinch of salt.
In a large mixing bowl, cream together butter and sugar until the mixture is light and fluffy. Incorporate the eggs and vanilla extract into the mixture.
Gradually mix the dry flour blend into the butter mixture until everything is well combined. Gently fold in the chocolate chips and walnuts.
Pour the brownie batter into the prepared baking dish, spreading it evenly.
Bake in the oven for approximately 25 minutes, or until the top is set and edges begin to pull away from the pan.