Step 1

Preheat the oven to 350F. Spray an 8x8-inch square baking pan with baking spray and line with parchment paper.

Step 2

In a small saucepan, melt the butter over medium heat. Remove from the heat and whisk in 1/2 cup chocolate chips. Continue whisking until fully melted. Transfer to a large bowl and let cool for a few minutes. (You can also melt the butter in a large bowl in the microwave, then stir in the chocolate until melted.)

Step 3

In another bowl, sift together the flour and cocoa powder. Whisk in the salt.

Step 4

To the melted chocolate, whisk in the sugars, eggs, and vanilla until smooth. Fold in the flour mixture until well combined. Fold in the remaining 1/2 cup chocolate chips. Pour the batter into the prepared pan and use a spatula to spread the batter to the edges of the pan.

Step 5

Drop the peanut butter over the top of the batter by teaspoonfuls. Use the tip of a knife or a screwer to swirl it into the batter.

Step 6

Bake for 40 to 45 minutes or until the center doesn’t wobble when the pan is gently shaken, or 35 minutes for a super fudgy center. Cover the brownies with foil after 25 minutes if the peanut butter appears to be browning. (The bake time may increase by 5 to 10 minutes if covered.) Let the brownies cool in the pan completely before slicing.