Preheat oven to 350F (175C) and line 13x9" metal baking pan with parchment paper. Set aside.
In a large mixing bowl, use an electric mixer to beat together butte, peanut butter, and sugars until smooth and creamy.
1 cup unsalted butter, 1 cup creamy peanut butter, 1 cup granulated sugar, 1 cup light brown sugar
Add eggs and vanilla extract and stir well.
2 large eggs, 2 teaspoons vanilla extract
In separate, medium-sized bowl, whisk together flour, baking powder, and salt.
2 ¾ cup all-purpose flour, 1 teaspoon baking powder, ½ teaspoons table salt
Gradually, on low speed, add flour mixture to peanut butter mixture, pausing occasionally to scrape down the sides of bowl.
Add milk and stir until combined.
2 Tablespoons whole milk
Spread batter into prepared ban and bake on 350F for 25-28 minutes (toothpick inserted in center should come back mostly clean or with only a few moist crumbs)
Allow to cool completely, then slice and brush with melted chocolate, if desired.
2 oz premium dark chocolate
Notes
StoringStore in an airtight container at room temperature for up to 3 days. Add-insFeel free to stir in up to 1 ½ cups of your favorite add-ins like milk chocolate chips or peanut butter chocolate candy pieces!