Ingredients

For the pies:

3 cups all-purpose flour
1 teaspoon baking soda
2 teaspoons unsweetened cocoa powder
1 1/2 cups canola oil
1 teaspoon white vinegar
One 1-ounce bottle red food coloring
1/2 teaspoon vanilla extract
1 1/2 cups sugar
2 eggs
1 cup buttermilk

For the filling:
5 tablespoons all-purpose flour
1 cup milk
1 cup sugar
8 tablespoons (1 stick) butter, softened
1/2 cup solid vegetable shortening, such as Crisco
1 teaspoon vanilla extract

Directions

Preheat the oven to 350°F. Lightly grease two cookie sheets. Sift the flour, baking soda, and cocoa together. In a separate bowl, combine the oil, vinegar, food coloring, and vanilla.

Using an electric mixer, beat the sugar and eggs together until they turn pale and double in volume. Add the oil mixture and beat to combine. Add the flour mixture and buttermilk alternately in five small additions, starting and ending with the flour.

Drop the batter by teaspoons onto the baking sheets, allowing 1 inch between drops, as the cookies will spread. You’ll be making 48 cookies. Bake until the cookies are firm but not crisp, about 12 minutes. Transfer immediately to racks to cool.

To make the filling, put the flour into a medium saucepan and slowly add the milk, whisking until smooth. Set over medium heat and cook, stirring constantly with a whisk, until very thick, about 3 minutes. Allow to cool completely.

Cream the sugar, butter, shortening, and vanilla with an electric mixer. Add the cooled flour mixture and whip until fluffy. Spread onto one cookie and top it with another to make a sandwich; repeat with the remaining cookies and filling. Cover the filled whoopee pies with plastic wrap and store in the refrigerator.