Preheat oven to 350 degrees F.
Grease square/round cup cupcake pan on all sides.
To Prepare Brownie Batter: Melt butter in small or medium saucepan.
Remove butter from heat and pour butter into large mixing bowl. Mix in sugar, eggs and vanilla until smooth. Mix in flour, cocoa powder, baking powder, and salt until well mixed. Set batter aside.
To Prepare Cookie Dough: Soften butter in microwave for about 20 seconds or until super soft, but not melted completely.
Cream together butter, white sugar, brown sugar, and peanut butter until smooth. Mix in egg until smooth. Stir in flour, salt, baking soda, and baking powder.
Baking: Fill cupcake cups about ¼ full with brownie batter. Put cookie dough on top of brownie batter until cups are about ¾ full. You don’t want to fill cups to top because they may overflow when baked. Repeat until all cupcake cups are full and batters are used.
Bake on 350 degrees F for 20 minutes or until toothpick when inserted comes out clean and cookie dough is lightly browned.Once baked, let cool.
To prepare glaze: In a double boiler over hot, but not boiling water, combine chocolate chips, butter, corn syrup, and milk. Once mixture is melted and smooth, mix in vanilla. Drizzle glaze over cooled brookies.