In a bowl combine the flour, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice. Mix well to combine.
In a separate bowl, combine the brown sugar and butter, beat together using an electric mixer until creamy, 1-2 minutes.
Add in the eggs, one at a time, beating the mixture after each one.
Add in the pumpkin puree, mixing by hand with a spatula.
Add half of the flour mixture to the wet ingredients, do not dump it in, rather take spoonfuls of the flour mixture and gently shake it over the wet ingredients, as if you were sifting in the flour. Fold in the mixture until no flour remains. Repeat with the other half of the flour, folding it in and scraping the sides and bottom of the bowl to incorporate everything.
Chocolate Cupcakes
In a small mixing bowl, combine the cocoa powder, flour, baking powder, baking soda and salt. Gently mix using a spoon.
In a larger mixing bowl, combine the butter and sugar, beat using an electric mixer until fluffy. Add in the eggs and vanilla, lightly beat.
Add in the sour cream and melted chocolate, mix by hand using a spatula.
Add half of the flour mixture to the wet ingredients, do not dump it in, rather take spoonfuls of the flour mixture and gently shake it over the wet ingredients, as if you were sifting in the flour. Fold in the mixture until no flour remains. Repeat with the other half of the flour, folding it in and scraping the sides and bottom of the bowl to incorporate everything.
Begin to add the batter into the pan, alternating between chocolate and pumpkin batters. Fill the cupcake liners almost completely full with batter.
Place the pan in the middle of the oven and bake for 15-17 minutes or until a toothpick inserted in the center comes out clean.
Allow the cupcakes to cool for about 3 minutes in the pan, then move them to a cooling rack.
Allow the cupcakes to cool completely before adding the frosting.
Pumpkin Buttercream
Place room temperature butter and vegetable shortening in a mixing bowl. Beat them together using an electric mixer until smooth, 1 minute.
Add in the pumpkin puree and pumpkin pie spice. Mix using a spatula.
Add in the powdered sugar, 1 cup at a time, mixing with a spatula at first so the powered sugar doesn’t puff up everywhere. Once all of the powdered sugar is incorporated, beat the buttercream using an electric mixer, 1-2 minutes or until smooth.
Chocolate Buttercream
In a mixing bowl, combine the butter and vegetable shortening, beat using an electric mixer until fluffy. Add in the cocoa powder, and gently mix by hand with a spatula. Begin to add the powdered sugar, about 1 cup at a time, mixing by hand. Continue adding powdered sugar until the frosting no longer looks wet and tastes good to you. Once all of the powdered sugar is incorporated, beat the buttercream using an electric mixer, 1-2 minutes or until smooth.
To frost the cupcakes
In a piping bag fit with a wilton 1M piping tip, do your best to add chocolate buttercream to one side of the bag and peanut butter buttercream to the other. Push the buttercream down into the bag. Pipe the buttercream onto the cupcakes, starting on the outside edge and working your way into the center, progressively stacking the frosting as you get to the center.
Notes
You will probably have extra buttercream, but I always like to have more than enough!