1. Preheat oven to 350 degrees F. Line 8×8″ square baking pan with parchment paper or foil. If using foil, spray it with cooking spray.
2. In medium bowl, combine flour, cocoa powder, and salt. Set aside.
3. In large mixing bowl, beat together butter, sugar, and vanilla until creamy.
4. Add the eggs one at a time.
5. Stir dry ingredients into batter.
6. Pour batter into prepared pan and spread evenly.
7. Sprinkle with chocolate chips. Bake in preheated oven for 22-25 minutes.
8. When brownie layer is done baking, combine peanut butter and oil in a microwave safe bowl or measuring cup and microwave on high for 20 seconds to soften.
9. Pour this warm mixture over hot brownie.
10. Sprinkle the peanut butter covered brownies with marshmallows.
11. Return to oven to bake for 3 more minutes, or until the marshmallows puff.
12. Sprinkle puffed marshmallows with toasted pecans.

Make the frosting:

1. To make frosting, in small saucepan, melt butter over medium heat. When butter is melted, add the cocoa powder and 1/4 cup of the milk and heat until the mixture begins to boil.
2. Remove from the heat and combine with confectioners sugar and salt in a separate bowl and beat on high speed with an electric mixer until smooth and glossy.
3. If frosting is not pourable at this point, add remaining 2 tbsp of milk (I didn’t have to do this).
4. Lastly, beat in vanilla, then pour evenly over puffed marshmallows.
5. Let cool completely in refrigerator for 1-2 hours.
6. Cut into squares and enjoy!