Preheat oven to 350 degrees.
Line a large square (9×9) pan with parchment paper.
In a small bowl whisk gluten free flour blend, baking soda, baking powder and cocoa.
Set aside.
In a medium saucepan add dark chocolate plus unsweetened squares and butter.
Heat on low heat until melted.
Stir.
Remove from heat and let cool slightly.
Add chocolate to bowl of stand mixer.
Mix white sugar into chocolate mixture.
Add eggs one at a time, beating after each addition.
Add vanilla.
Add dry ingredients and mix on medium speed until just combined.
Add chocolate chips plus nuts.
Stir.
Pour batter into square baking pan.
Bake for 30-35 minutes.
Let cool completely if making the 3 layer brownie.
If making this as a stand alone, you can enjoy a warm brownie if you’d like.