For the chocolate tombstones: Melt black baking chips in the microwave. Melt on high in 30 second intervals, stirring each time until completely melted. Use a silicone basting brush to paint the molds first, this will help to prevent bubbles or cracks. Then pipe the rest of the chocolate into the mold and use a knife to smooth out and remove any excess candy. Put the mold into the freezer for about 30 minutes or until candy is frozen solid.
For the cupcakes: Preheat oven to 350° F. Line cupcake tins with paper cups.
In a medium bowl combine the flour, Davis Baking Powder, baking soda and salt. Set aside. In a separate bowl, combine the vanilla extract and buttermilk. In a large bowl, cream the butter and sugar until fluffy. add the eggs one at a time and beat until combined. With the mixer on low speed, add the flour mixture in 2 equal portions, alternating with the buttermilk mixture, starting and ending with the flour mixture. Mix after each addition until JUST combined.
Divide the batter evenly among the cupcake tins, filling each about 2/3 full. Bake the cupcakes for 20 - 30 minutes. To test for doneness, insert a toothpick in the middle of a few cupcakes at a time and remove. Take the cupcakes immediately from the oven in their pan to a wire cake rack and let them sit for 5 minutes before turning out onto the rack to cool right-side-up.
For the buttercream frosting: Beat the butter until smooth and fluffy, it should visibly lighten in color. Add the powdered sugar, 1/2 cup at a time, and beat until incorporated. Add 2 tablespoons of the heavy cream and beat well on medium speed. Add the vanilla extract. If the mixture is too stiff, add more milk until the mixture is firm and creamy. Reserve 2-3 Tbsp. of frosting to use as grass (if desired)
For assembly: When the cupcakes are completely cooled, Use a knife to cut a shallow slit in the top of the cupcake for the tombstone to sit in. Pipe buttercream frosting on top. Decorate with green buttercream, candy pumpkins and crushed cookies or chocolate sprinkles.