Preheat oven to 350°
Butter a 9"x13" baking pan and dust with cocoa powder.
In medium to large mixing bowl, melt butter. Using hand or stand mixer, blend in sugar for about 1 minute and then vanilla.
Add eggs one at a time, mixing well after each addition.
Add cocoa to butter and egg mixture and mix on low until incorporated.
Next, add flour, baking powder and salt to the top of the ingredients already in the bowl. I like to blend them loosely with a fork before turning on the mixer to bring them all together. Then, turn on mixer and mix for about a minute until everything looks blended.
Add both kinds of chocolate chips and mix on low.
Pour batter into prepared pan.
Bake for 30-35 minutes checking when you first smell the brownies likely around 25 minutes. Bake until cake tester or toothpick comes clean.
Cool completely and cut into squares.