Preheat oven to 350 degrees F and line an 8-inch square pan with parchment paper and grease well
In a small saucepan set over medium low heat, melt the butter. Stirring occasionally, continue to cook the butter, increasing the heat to medium. You will see after a few minutes the butter develops a nutty aroma and brown bits start to form at the bottom. Once the bits are amber (about 2-3 minutes later), remove from heat
Add in 4 ounces of dark chocolate and stir until melted
In a large bowl, combine coconut sugar, eggs, and vanilla and mix until completely combined
Gradually pour in the warm brown butter chocolate mixture into the bowl and continue to mix
Stir in flour and cacao powder until just combined then stir in the chocolate chips
Pour into prepared pan and smooth out with a spatula
Bake in the oven for 22 to 25 minutes then let cool in pan completely before slicing and serving
Notes
*Store in airtight container for 5 days or freezer for 2 months