To make the pies, preheat the oven to 350˚F. In a medium-sized bowl, whisk the flour, baking powder, baking soda, and salt together and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, combine the shortening, butter, and sugar, and mix on medium-low speed until slightly fluffy, scraping down the bowl with a rubber spatula, as needed. Add the yolks and vanilla and mix until just incorporated.

Place the cocoa and espresso powders in a small bowl and add the boiling water. Whisk until combined and add to the stand mixer bowl. Mix on medium low to combine.

Add the dry mixture in three additions, alternating with the buttermilk in two. Stop the mixer when there is still unincorporated flour in the dough and finish mixing by hand. Let the dough rest on the counter, lightly covered with plastic wrap, for at least 30 minutes.

Line two baking sheets with parchment paper and drop 1 ½ tablespoons of dough about 1 inch apart on the sheets. Bake for 8 to 10 minutes, rotating the pans halfway through the baking time until the cookies are dry to the touch and bounce back when lightly pressed. Let cool completely before filling.

To make the peppermint filling, place the butter in the bowl of a stand mixer fitted with the paddle attachment and beat on low to medium-low until smooth, about 3 minutes. Begin adding the sugar, ½ cup at a time, alternating with a tablespoon or two of the cream, until all of the sugar and cream has been added. Stop the mixer and scrape the bowl with a rubber spatula, as needed.

Add the peppermint and salt, and continue mixing on medium-low for at least 5 to 10 minutes, if not longer. The frosting will be quite light, creamy, and fluffy when it is done. Add a few drops of the food coloring, and mix until just incorporated.

Store the frosting tightly covered at room temperature for up to 24 hours or refrigerate it for up to one month. Bring the frosting to room temperature prior to using.

Place the sparkling sugars in two shallow bowls and roll the edges of half of the pies in one, and half in the other.

Serve whoopies immediately, or freeze on a cookie sheet, covered with plastic wrap, for up to three weeks. Bring to room temperature before serving.