For the Brownie Cookies:

1. Preheat the oven to 350F. Line a baking sheet with parchment paper.
2. In a small saucepan over low heat, melt the butter and chocolate, stirring until smooth.
3. In the bowl of a stand mixer with the whisk attachment, whisk the eggs, sugar and vanilla until creamy.
4. Sift the flour, powdered sugar, baking powder and cocoa powder, and add to the egg mixture. Folding with a spatula, add the melted chocolate mixture and stir until fully incorporated.
5. Chill for 15 minutes.
6. With a small cookie or spoon, spoon dough onto prepared sheet. Slightly flatten the tops by pressing down with your fingers, so that they look more like discs.
7. Bake for 10-12minutes, until the tops crackle. Allow to cool completely.

For the Peanut Butter Frosting:

1. In the bowl of a stand mixer with the paddle attachment, beat the butter and peanut butter on medium speed until smooth, about 2 minutes.
2. Gradually mix in the powdered sugar, and continue beating. Add vanilla extract and salt.
3. As the mixtures starts getting thick, add 1 tbsp of heavy cream at a time until desired consistency. I used about 4 tbsp for a creamy and spreadable frosting. Beat for another 2 minutes until light and fluffy.
4. Cover and refrigerate until ready to use.
5. To assemble the cookies, using a spoon or pastry bag, spread the frosting on one side of the cookie. Place another cookie on top and gently press down.
6. Enjoy!