For Chocolate Cookies: Preheat oven to 375 degrees F (190 degrees C) and place oven rack in the center of the oven. Line two baking sheets with parchment paper.

In a large bowl sift together the flour, cocoa powder, baking powder, baking soda, and salt.

In the bowl of your electric mixer, fitted with the paddle attachment (can also use a hand mixer), beat the butter and sugar until light and fluffy. Add the egg beating well. Beat in the vanilla extract. In a small measuring cup, mix the buttermilk and coffee (or water). With the mixer on low speed, alternately add the flour mixture and buttermilk/coffee mixture, in three additions, beginning and ending with the flour. Drop heaping tablespoons (can also use a small ice cream scoop) of the batter onto the prepared baking sheets, spacing about 2 inches (5 cm) apart. With moistened fingers or with the back of a spoon, smooth the tops of the cookies.

Bake for about 9-10 minutes or until the tops of the cookies, when lightly pressed, spring back. Remove from oven and transfer to a wire rack to cool completely.

Filling: Beat the shortening and butter until soft and creamy. With the mixer on its lowest speed, gradually beat in the confectioners' sugar. Increase the speed to high, and beat until light and fluffy, about 3-5 minutes. Then, with the mixer on low speed, beat in the vanilla extract and slowly drizzle in the corn syrup. Continue to beat until the filling looks like soft mayonnaise. 

To Assemble: Take one cookie and spread a heaping tablespoon of the filling on the flat side of the cookie. Top with another cookie.

The assembled cookies can be stored, covered, in the refrigerator for several days. Serve cold or at room temperature.

Makes about 15 sandwich cookies.

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Whoopie Pies:

1 3/4 cups (230 grams) all purpose flour

3/4 cup (75 grams) Dutch-processed cocoa powder

1 teaspoon baking powder

1/4 teaspoon baking soda

1/4 teaspoon salt

3/4 cup (170 grams) unsalted butter, room temperature

3/4 cup (150 grams) granulated white sugar

1 large egg, room temperature

1 teaspoon pure vanilla extract

1/4 cup (60 ml) buttermilk

1/2 cup (120 ml) lukewarm strong coffee or !/2 cup (120 ml) lukewarm water

Vanilla Filling:

1/4 cup (55 grams) vegetable shortening

1/4 cup (4 tablespoons) (55 grams) unsalted butter, room temperature

1 cup (115 grams) confectioners' (powdered or icing) sugar, sifted

1 1/2 teaspoons pure vanilla extract

1/2 cup (120 ml) light corn syrup