In a medium-sized bowl, whisk the brown sugar, granulated sugar, and egg yolks until fully combined and smooth.
Whisk in the milk and vanilla.
Fold in the peanut butter with a rubber spatula, mixing for about 2-3 minutes to until fully incorporated.
Using a one tablespoon cookie scoop, scoop the cookie dough onto one baking sheet lined with parchment paper. Freeze cookie dough for 15 minutes.
After 15 minutes, divide each dough ball in two (I weighed mine out to be ~14g each), then roll each ball in the sugar, gently squish the two together, and place on a parchment lined baking sheet.
Dip a fork in water then in sugar and use to make a criss-cross indentation in each cookie dough ball. Freeze for another 15 minutes.
While the cookie dough is freezing for the second time, preheat the oven to 325 degrees.
Bake the cookies for about 12-15 minutes. Allow to cool completely on the baking sheet.
For the peanut butter frosting:
In the bowl of a stand mixer fitted with a paddle attachment, cream the butter until smooth.
Add the peanut butter and mix until fully combined.
While mixing on low speed, slowly add the powdered sugar.
Turn the speed up to medium, then add the salt and the heavy cream and beat until smooth.
For the chocolate:
In a small heat proof bowl, add the chocolate and neutral oil.
Microwave in 20 second intervals, stirring in between, until fully melted and smooth.
For assembly:
Pair the peanut butter cookies up and spread the frosting on the bottom cookies, then press the paired cookie on top.
Dip each in the melted chocolate and enjoy!
Notes
I recommend only using a thick, creamy peanut butter like Jif or Skippy.
You can store the cookie dough or baked cookies in the freezer for up to 3 months.