• Preheat the oven to 375 degrees Fahrenheit. Line a rimmed half cookie sheet (13x18x1) with parchment paper, or spray with nonstick spray. 
• In a large bowl, combine the old fashioned oats, flour, baking powder, and salt. Set aside.
• In a large mixing bowl, mix together your peanut butter and butter. 
• Add in the sugar and brown sugar and cream together till smooth, and light. 
• Add in the eggs, and vanilla and stir to combine. 
• Add the dry ingredients to the wet ingredients and stir it all together. 
• Press the cookie dough into the cookie sheet, spreading evenly to the edges. The dough is pretty sticky, so spray your hands or a rubber spatula with nonstick spray while you spread it. 
• Bake in the preheated oven for 15 minutes, until the middle is just barely set. 

For Topping the Bars:

• Allow the bars to cool for about 5 minutes, then drop peanut butter dollops over the top of the bars. 
• Allow to sit for about 1-2 minutes until the peanut butter starts to soften, then spread the peanut butter evenly over the top. 
• In a medium sized heavy sauce pan over medium heat, add butter, cocoa powder and milk. Bring to a boil.
• Remove from heat and whisk in powdered sugar till smooth.
• Spread chocolate frosting over the top of the bars and spread into an even layer. 
• Allow frosting to set and bars to cool completely before cutting into squares to enjoy. 
• Store bars in an airtight container at room temperature for 5-6 days.