Preheat the oven to 350 F. Grease an 8x8 baking dish with butter or nonstick cooking spray, or line with parchment paper. Set aside.
Add the melted butter, granulated sugar, brown sugar, and vanilla extract to a large mixing bowl. Stir (using a spoon - no electric mixers) until fully combined.
Add in the milk, and then the eggs one at a time. Stir until just combined.
In a separate medium-sized bowl, combine the dry ingredients (flour, cocoa, baking soda, and salt). Add the dry ingredients to the wet in intervals, mixing until smooth.
Optional: Fold in the chopped nuts or chocolate chips if using, reserving ¼ cup.
Allow the batter to rest for 10 minutes. This allows the rice flour to absorb the moisture, reducing any possible grittiness.
Pour the batter into the prepared pan and smooth the top with a silicone spatula. Sprinkle the remaining ¼ cup of toppings over top.
Bake for 30-40 minutes, or until a toothpick inserted into the center comes out clean and the edges are crispy. Allow the brownies to cool in the pan for at least 15 minutes before cutting into squares, ideally longer if you want clean cuts.
Enjoy!
Notes
Homemade Gluten Free Brownies are best stored in an airtight container at room temperature for 2 to 3 days.You can also freeze these brownies. Once ready to eat, set out a brownie and let thaw at room temperature for 30 minutes, or overnight in the fridge. Additionally, you can warm the gluten free brownies in the microwave for 10-30 seconds.