Place liners in muffin tin. Preheat oven to 350° F.
In a mixing bowl, combine flour, sugar, baking powder, cocoa powder, baking soda, and salt.
In a separate mixing bowl, mix oil, vanilla, and buttermilk. Add this mixture slowly to your dry ingredients while stirring constantly. Stir in the coffee and mix thoroughly
Add batter into muffin cups, about ¾ full.
Bake the batter for about 22 minutes, or until a toothpick comes out clean when inserted. Set aside.
For the buttercream, combine all the ingredients in a mixing bowl. Beat until it becomes smooth.
Pipe the buttercream onto the cupcake. Top with chocolate syrup and sprinkle with peanuts or chocolate chips as desired.