Melt the butter on high for about 30 to 40 seconds. Add the sugar, cocoa and vanilla and mix together with a whisk until well combined.
Add the eggs, one by one, whisking after each one is added then sift in the flour and add the chocolate chips and fold everything together.
Grease an 20x14cm pyrex dish and spoon in half of the brownie mixture. Cook on high for 3 ½ minutes (the more powerful your microwave the less time it takes). Let rest for 5 minutes before removing from the dish. Then dust both brownies with cocoa powder before serving in squares.
