Preheat the oven to 350˚F.
Add the butter and 1 cup of chocolate chips to a large microwave-safe bowl.
Microwave for 1 to 1½ minutes, then let sit for 3 minutes before whisking together.
Add in the granulated and brown sugars, vanilla, and salt. Whisk to combine.
Whisk in the eggs until fully combined.
Sift the flour and cocoa powder into the bowl and fold in with a spatula. A
dd 1 teaspoon of flour to the remaining chocolate chips and toss.
Add these chocolate chips to the mix.
Line a 9-inch square baking pan with parchment paper and grease with butter. Spread the batter evenly in the pan.
Bake for 30 – 40 minutes, until a toothpick inserted in the center, comes out with a few moist crumbs attached. Cool for about 1 hrs.