Creating Peanut Butter Stuffed Brownies is simple if you follow these easy steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking pan with cooking spray or line it with parchment paper for easy removal.
2. Mix the Wet Ingredients: In a large mixing bowl, combine the melted butter and granulated sugar. Stir until well combined. Add the eggs and vanilla extract, mixing until smooth.
3. Combine Dry Ingredients: In another bowl, sift together the flour, cocoa powder, baking powder, and salt.
4. Combine Mixtures: Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix; it’s okay if there are a few lumps.
5. Prepare the Peanut Butter Filling: In a separate bowl, mix the creamy peanut butter with powdered sugar (if using) until smooth and creamy.
6. Layer the Brownie Batter: Pour half of the brownie batter into the prepared baking pan, spreading it evenly.
7. Add the Peanut Butter Filling: Spoon the peanut butter mixture over the brownie batter, spreading it out as evenly as possible.
8. Top with Remaining Batter: Pour the remaining brownie batter over the peanut butter layer, spreading it gently to cover the filling.
9. Bake: Place the pan in the preheated oven and bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
10. Cool: Remove the brownies from the oven and let them cool in the pan for about 15 minutes before transferring them to a wire rack to cool completely.
11. Slice and Serve: Once cooled, cut the brownies into squares and enjoy!