Preheat oven to 350 degrees F and line a 9 x 9-inch baking pan with overhanging layers of parchment paper. Set aside.

In a microwave-safe bowl, combine 1/2 cup butter and chocolate chips. Microwave in 30-second increments, whisking after each, until completely smooth. Then mix in the granulated sugar until completely combined; whisk in the eggs and vanilla.

With a spatula or spoon fold in the flour, cocoa powder, baking powder, and salt. Set aside.

For the Peanut Butter Swirl: Melt butter in a medium-size bowl and add a few drops of yellow and red food coloring, until the butter has a nice orange color. Add the peanut butter and confectioners sugar and mix together until smooth.

Drop big spoonfuls of the chocolate brownie batter randomly into the prepared pan. Top with spoonfuls of the peanut butter batter. Using a knife, swirl the batters together. Sprinkle with additional chocolate chips.

Bake 30 to 35 minutes or until a toothpick inserted in center comes out mostly clean. Cool completely; about 1 hour. For 16 brownies, cut into 4 rows by 4 rows.