For Whoopie Pies:
1 cup butter
1/2 cup dark chocolate chips
2-1/2 cups all-purpose flour
1/4 cup dark cocoa
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup granulated sugar
3/4 cup sour cream
2 large eggs
1 tablespoon white vinegar
1 teaspoon pure vanilla
1 tablespoon red food coloring
For Cream Cheese Butter Cream Filling:
1-1/2 cups butter, room temperature
1/2 cup cream cheese, room temperature
4 cups powdered sugar
1/2 cup whole milk
2 tablespoons pure vanilla
In a small saucepan over low heat, melt the butter and chocolate (or melt in the microwave for about 30 seconds on high). Set aside to cool.
Onto a large piece of parchment paper, sift together the flour, cocoa, baking powder, baking soda and salt. Set aside.
In a large bowl, whisk together the sugar, sour cream, eggs, vinegar and vanilla to combine. Add the red food coloring and whisk gently. Add the melted chocolate and whisk to combine. Sprinkle the dry ingredients over the batter and whisk until well combined.
Use the ice cream scoop to drop the batter in 10 equal portions onto the prepared cookie sheets, about 1-1/2 inches apart.
Bake in the preheated oven for 12 to 15 minutes or until the tops spring back when lightly pressed.
Meanwhile, prepare the Cream Cheese Butter Cream. In a stand mixer fitted with a paddle attachment, beat the butter and cream cheese on high speed until very pale in color. Scrape down the sides of the bowl at least twice while beating to make sure the butter and cream cheese are evenly combined. Turn the mixer on low and slowly add the powdered sugar. Mix until well combined then slowly add the milk and vanilla. Scrape down the sides of the bowl again. Turn the mixer to high and let it run for at least 10 to 12 minutes, until the butter cream is light and fluffy.
Remove the cookies from the oven and cool slightly on the cookie sheets, then transfer to wire racks to cool completely.
Turn half of the cookies bottom side up. Use the piping bag or two spoons to add a heaping tablespoon of butter cream onto each. Place the remaining cookies on top, right side up, and gently press to sandwich the two together.
The whoopie pies will keep in an airtight container for several days.