Using a double boiler method, melt butter and chocolate chips. Keep it aside. Let this cool for 10 minutes.
½ cup Butter, 1 ⅓ cups Semi-sweet chocolate chunks or Chocolate chips
Preheat the oven to 350 degrees F. Line 8 * 8 or 9 *9 baking pan with parchment paper and keep this aside.
In a bowl, add egg and salt and whisk until light and foamy. To this, add white sugar, brown sugar, and vanilla extract and whisk until smooth.
2 Eggs, ½ teaspoon Salt, ⅔ cup White sugar, ⅓ cup Brown sugar, 1 ½ teaspoon Vanilla extract
To this, add the cooled melted chocolate-butter mixture and mix.
Add the cocoa powder and mix using a whisk. Finally, add flour and baking powder and mix using a whisk. Do not overmix.
⅓ cup Cocoa powder, ½ cup Flour, ¼ teaspoon Baking powder
Pour the batter into the prepared pan and smoothen the top. Add the dollops of peanut butter on top. Swirl it into the batter.
¼ cup + 2 tablespoon Peanut butter
Bake for 20 to 25 minutes. Remove and let it cool for 1 hour. Once cooled completely, cut them into squares of desired size.