Melt ¼ cup chocolate melting wafers. Using a dollop of melted chocolate, stick a chocolate kiss to one side of the peanut butter cookie. Repeat with remaining cookies. Let the chocolate set.
Using another dollop of the melted chocolate, stick a chocolate chip to the other side of the peanut butter cookie. Repeat with remaining cookies. Set aside to allow chocolate time to set.
Cupcakes
Preheat oven to 400℉. Sift the flour and sugar together in a large mixing bowl and set aside.
Combine oil, butter, water, and cocoa powder in a saucepan. Bring to a boil, stirring to combine. Add to the flour/sugar and stir to fully combine. Add buttermilk, vanilla, baking soda, and salt. Stir to combine. Add in eggs and mix until fully combined.
Spoon the batter into the cupcake liners. Fill ⅔ full with batter. Bake for 15 minutes until a cake tester comes out clean. Let cool before frosting.
Frosting
Add butter and peanut butter to the bowl of an electric mixer fitted with a whisk attachment. Mix until well combined. Slowly add the sifted powdered sugar and salt. Add 4 tablespoons of the heavy cream and mix until well combined and creamy. Add remaining 2 tablespoons of cream, as needed, to achieve a light and fluffy consistency.
Spoon the frosting into a pastry bag fitted with a star tip. Pipe frosting onto the cupcakes. Adorn the top with a chocolate peanut butter acorn.