Mix your flour, baking soda, coca and salt together. Set aside.
In another bowl, blend together the butter, sugar, eggs, and hazelnut extract. Alternately add the dry ingredients to the wet ingredients with 1 cup of milk. Stir until no lumps remain, but don’t over mix.
Line your muffin tin with cupcake liners; fill 1/2-3/4 full. Bake at 350 for 15-20 minutes or until tests done. Remove from the tins and let cool completely on a wire rack.
For the frosting, whip the butter until nice and cream; then add the milk, powdered sugar, peanut butter, and vanilla extract. Mix until creamy and frosting consistency. You can add a little more milk if it’s too thick or a little more powdered sugar if it’s too thin.
Frost the cupcakes and top with a peanut butter cup or two on each. Melt the semi sweet chocolate chips and drizzle over the cupcakes.