Preheat oven to 350 degree F. Line 16 cupcake cups with liners.
Using a double boiler melt the chocolate and espresso powder together. Stir consistanly. Remove from heat and let cool.
In large bowl whisk together the flour, sugars, baking soda, salt, cinnamon and nutmeg.
Make a well in the center of flour mixture.
In medium bowl whisk together the pumkin, eggs, oil, buttermilk and vanilla. Add to the dry ingredients.
Stir until just combined.
Spoon 1 1/2 cups batter into a seperate bowl and stir in the cooled chocolate expresso mixture.
Using a cookie scoop, scoop pumkin batter into each cupcake liner. Using back of spoon make a well in the pumpkin batter.
Place a scoop of chocolate mixture into the cupcake liner into the well of the pumpkin batter. Each cupcake should be filled 2/3 of the ways with batter. Swirl the two batters together with a toothpick.
Bake 20-25 minutes until toothpick inserted comes out clean.
Let cool completely.
BUTTERCREAM:
In bowl of mixer cream the butter until light and creamy.
Add in the confectioners sugar one spoonful at a time, alternate with milk as needed. Add in the espresso powder, vanilla and salt.
Mix until well combined.
ASSEMBLY:
Arrange cupcakes so they are ready for buttercream. Pipe buttercream on top of each cupcake. If adding the sprinkles to the edges do so one cupcake at a time so the buttercream is still soft or they will not stick.