Preheat your oven to 350 degrees. Line one giant (11″) cookie pan with parchment paper, then set it aside (NOTE: I usually just cut out a large circle for the bottom).
In the bowl of a stand mixer fitted with the paddle attachment, beat together sugars, butter and peanut butter until smooth, about 2-3 minutes. With mixing speed on low, add vanilla, heavy cream and one egg. Mix until incorporated, then add the remaining egg.
In a medium size mixing bowl, whisk together flour, baking soda, baking powder and salt. With mixing speed on low, gradually add the dry ingredients, mixing until no visible dry ingredients remain. Remove the bowl from the stand and gently fold in the M&M’s (or peanut butter cups), peanut butter chips and chopped peanuts.
Using a spatula, place the dough into the pan, pressing to create an even layer. Place the pan in oven and bake for 16-20 minutes or until the edges become golden brown in color. Remove from the oven and allow to cool for 45 minutes before frosting.
Meanwhile, to prepare the frosting, beat all ingredients together in a medium size mixing bowl for 3 minutes or until the mixture becomes light and fluffy. Place the frosting into a piping bag fitted with desired tip and then pipe onto the cooled cookie (around the edges or in the center if you want to write something on it).