01 -
Preheat oven to 325°F (163°C). Line an 8x8-inch pan with parchment or foil and set aside.
02 -
In a microwave-safe bowl, combine butter and sugar. Heat in the microwave on HIGH for about 1 minute and 15 seconds. Remove, stir, and cool on the counter for 5 minutes, then stir in the vanilla extract and cocoa powder.
03 -
Transfer the warm (but not hot) butter/sugar mixture to the bowl of a stand mixer. With the mixing speed on low, add one egg at a time, mixing just until incorporated.
04 -
In a medium-sized mixing bowl, whisk together flour, baking soda, cornstarch, and salt. With mixing speed on low, gradually add the dry ingredients to the wet mixture. Mix until no flour pockets remain.
05 -
Remove the bowl from the stand mixer and fold in the chocolate chips and chunks.
06 -
Spread the brownie batter evenly into the prepared pan. Bake for 20-30 minutes or until the brownies are set. Remove from oven and allow to cool for 30-45 minutes before cutting and serving.