pumpkin chocolate cupcakes

the goods:

chocolate batter:
1 and 1/3 cups flour
1/2 cup cocoa powder
1 teaspoon baking soda
1 teaspoon instant espresso powder
1/4 cup canola oil
2 teaspoons vanilla extract
1 cup light brown sugar
1 and 1/3 cups buttermilk
4 egg yolks (save whites for pumpkin batter)

pumpkin spice batter:
2 cups (scant) flour
2 teaspoons baking powder
1/2 teaspoon baking soda
1 teaspoon salt
2 teaspoons cinnamon
1 teaspoon nutmeg
1 teaspoon ground ginger
4 egg whites
2 cups pumpkin puree
1 cup light brown sugar
3/4 cup canola oil
3/4 cup granulated sugar

vanilla bean buttercream:
1 cup (2 sticks) unsalted butter, room temperature
6 cups powdered sugar
2 vanilla beans, scraped
1 teaspoon vanilla extract
pinch of salt
6 tablespoons heavy cream

Preheat oven to 350 degrees, and line two 12-cup muffin pans with paper liners.
Make the chocolate batter by combining the flour, cocoa powder, baking soda, and espresso powder in a large bowl. Whisk together, then make a well in the center of the dry ingredients and add the oil, vanilla, brown sugar, buttermilk, and egg yolk. Stir together with a wooden spoon until combined. Set aside.
Make the pumpkin batter by combining the flour, baking powder, baking soda, salt, and spices. Whisk together, then make a well in the center and add egg whites, pumpkin, brown sugar, oil, and granulated sugar. Stir together with a wooden spoon until combined. Set aside.
Using a small cookie scoop (1 tablespoon), drop a dollop of chocolate in the bottom of each paper liner. Next, drop a dollop of pumpkin batter on top of each chocolate layer. Continue with another dollop of chocolate and another dollop of pumpkin until all the cups are filled and the batter is used up.
Bake the cupcakes for 17-20 minutes, or until a toothpick inserted in the center of one of the cakes comes out clean with a few moist crumbs attached. Let the cupcakes cool in the pan for 1 minute before removing to wire racks to cool completely.
To make the frosting, beat the butter in a stand mixer until light and fluffy, about 1-2 minutes. Slowly add the powdered sugar, vanilla bean, vanilla extract, and salt while continuously beating. Add the heavy cream 1 tablespoon at a time until completely incorporated. Scrape the bowl down and whip for 1 minute more until light and fluffy.
Frost cooled cupcakes with the vanilla bean frosting and serve.