Step 1

Preheat the oven to 325 degrees F, mist a 9x9-inch or 9x13-inch pan with non-stick spray, and line it with a sheet of parchment.

Step 2

Place the sugar, cocoa, and butter in a large microwave-safe bowl,* and microwave in one-minute increments, stirring, until the butter is completely melted and the mixture feels quite hot to the touch (approximately 3 to 4 minutes).

Step 3

Add the eggs, one at a time, stirring vigorously after each addition.

Step 4

Fold in the flour, baking powder, and salt until just a few streaks remain.

Step 5

Stir in about 2/3 of the chocolate chips and vanilla, and transfer the batter to the prepared pan.

Step 6

Sprinkle the remaining chocolate chips on top , and bake until set around the edges but still soft towards the middle (approximately 30 to 45 minutes).

Step 7

Cool completely in the pan, then transfer to a cutting board and cut into squares.