Preheat oven to 350 degrees. Spray a glass 9x9 square pan with non stick cooking spray and set aside.
In a small pot, melt butter, chocolate chips and cocoa together over medium low heat, stirring until smooth. Remove from heat and stir in sugar. Stir in eggs, 1 at a time and vanilla. Gently stir in all dry ingredients until just incorporated. Pour into prepared pan and bake 20-30 minutes or until just set. Mine was done right at 20 minutes, but my oven is also hotter than the sun. Set aside to cool.
For the frosting, stir butter, cookie butter, vanilla and powdered sugar together until a thick paste forms. Stir in milk carefully and then mix vigorously to smooth out any lumps. Spread over brownies, cut into bars and serve.