Once the peanut butter is frozen, remove the layer from the pan and return it to the freezer until the brownie batter is prepared. Preheat the oven to 350 F (177 C). Line an 8x8 pan with parchment paper along the bottom and two sides.
In a microwave safe mixing bowl add the butter and ½ cup (85 g) of chocolate chips. Heat in 30 second increments, stirring after each until the butter and chocolate are fully melted and mixed together.
Evenly scoop half of the brownie batter into the prepared pan. Remove the frozen peanut butter layer from the freezer. Gently lay the peanut butter layer on top of the brownie batter and gently pull the parchment paper off the peanut butter. Top with the remaining brownie batter and remaining ¼ cup peanut butter.
Bake for about 45 - 50 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. Cool the brownies in the pan for 30 minutes. Lift the brownies from the pan to fully cool on a cooling rack. Slice the brownies and enjoy!