Preheat your oven to 350°F (175°C). Prepare your brownie mix according to package instructions or your preferred recipe, then pour the batter into a greased 8-inch baking dish. Bake for approximately 25 to 30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Allow the brownies to cool in the pan while you prepare the peanut butter filling.

In a medium mixing bowl, combine softened peanut butter, butter, and powdered sugar. Beat the mixture with a hand mixer on medium speed for about 2-3 minutes, until creamy and smooth. If you desire a thinner consistency, gradually add milk, mixing until you achieve your preferred thickness. Set aside the peanut butter filling while your brownie base cools completely.

Once the brownie base has cooled, use a spatula to evenly spread the creamy peanut butter filling over the top. Start from one edge and work your way across, smoothing it out to cover the entire surface of the brownies.

In a microwave-safe bowl, combine chocolate chips with a splash of oil. Microwave in 20-second intervals, stirring in between until fully melted and smooth. Drizzle or spread the melted chocolate over the peanut butter filling using a spoon or spatula.

After applying the chocolate coating, place the brownies in the refrigerator for about 30-60 minutes to allow the layers to set and firm up. Once chilled, remove the brownies from the pan and cut them into squares.