Stir together butter, sugars, peanut butter, and vanilla until evenly distributed. Add eggs to mixture.
In a separate bowl, stir together flour, salt, and baking powder. Gradually incorporate dry ingredients into peanut butter mixture. Add milk to mixture and mix until smooth.
Transfer batter to a greased 9x13 baking pan.
Bake for 50-55 minutes.
Allow to cool. Drizzle with melted white chocolate.
Recipe by Rachel Schultz at https://rachelschultz.com/2016/06/16/peanut-butter-brownies/