Step 1

Preheat oven to 350°.

Step 2

Cream together butter, peanut butter and sugars. Cream for 3 minutes, the mixture will be light and fluffy.

Step 3

Scrape the sides of the bowl and add in the eggs and vanilla. Mix until combined.

Step 4

Add the flour, salt and rolled oats to the bowl and mix thoroughly.

Step 5

Scoop the cookie dough out onto a parchment paper lined cookie sheet.

Step 6

Bake for 8-10 minutes, or until the edges barely start turning brown. The cookies probably won't change shape much while cooking, that is okay.

Step 7

Right after the cookies are pulled out of the oven, take the back of a glass drinking cup and smash the cookies flat. Let them cool on the hot pan.

Step 8

Place all ingredients into the bowl of a stand mixer.

Step 9

Using the paddle attachment, starting slowly, combine the ingredients.

Step 10

Once the ingredients are mostly combined, turn the speed up as high as possible and let the buttercream whip for a few minutes until light and fluffy.

Step 11

Each sandwich will use two cookies.

Step 12

Frost the backside of one cookie with a generous amount of frosting.

Step 13

Top the frosting with another cookie. The backsides of the cookies should be touching the frosting, so the pretty side of the cookie is facing out.