Preheat oven to 350 degrees. Line a 9x13 pan with parchment paper. Set aside.
In a bowl combine melted butter and cocoa powder. Mix on medium speed.
Add the eggs and beat until thickened and smooth.
Now add the sugar and mix until well combined, then add the flour and mix another 2 minutes.
Spread the mixture into the pan and bake for 20 minutes until center is set. Top the brownies mixture with mixed nuts. Allow brownies to cool down before serve.