• Preheat oven to 350 degrees F. Line 8x8" square baking pan with parchment paper or foil. If using foil, spray it with cooking spray.
• In medium bowl, combine flour, cocoa powder, and salt. Set aside.
• In large mixing bowl, beat together butter, sugar, and vanilla until creamy.
• Add the eggs one at a time.
• Stir dry ingredients into batter.
• Pour batter into prepared pan and spread evenly.
• Sprinkle with chocolate chips. Bake in preheated oven for 22-25 minutes.
• 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.
• Pour this warm mixture over hot brownie.
• Sprinkle the peanut butter covered brownies with marshmallows.
• Return to oven to bake for 3 more minutes, or until the marshmallows puff.
• Sprinkle puffed marshmallows with toasted pecans.

Make the frosting:

• To make frosting, in small saucepan, melt butter over medium heat. When butter is melted, add the cocoa powder and ¼ cup of the milk and heat until the mixture begins to boil.
• 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.
• If frosting is not pourable at this point, add remaining 2 tablespoon of milk (I didn't have to do this).
• Lastly, beat in vanilla, then pour evenly over puffed marshmallows.
• Let cool completely in refrigerator for 1-2 hours.
• Cut into squares and enjoy!