Makes 40 to 50 individual cookies depending on size
For the Meringues:
For the Frosting:
11 ounces good dark chocolate, chopped
Preheat the oven to 350 degrees F. Line 2 baking sheets with parchment paper.
Make the meringue. Whip the egg whites in a large bowl with an electric mixer on high speed until frothey. Gradually add the sugar, 1 to 2 tablespoons at a time, and continue whipping until the egg whites form stiff peaks, about 10 minutes. Gently fold in the almond flour. Using two spoons or a pastry bag fitted with a large plain tip, spoon or pipe the egg whites onto the parchment-lined baking sheets. The meringues should be 1 1/2 to 2 inches wide and 1/3 to 1/2 inch high.
Bake until crisp, 10 to 12 minutes. Let cool on the baking sheets for 8 to 10 minutes, then transfer to a wire rack to cool completely. Transfer the cooled meringues to a plate, cover with plastic wrap, and freeze while you make the frosting.
Make the frosting. With a wooden spoon, in a medium bowl, mix the sugar with the butter until smooth. Whisk the egg yolks in another medium bowl until pale and thick, then gradually stir into the butter mixture. Pour in the dissolved coffee, add the cocoa powder, and mix until the frosting is smooth and thick. Cover with plastic wrap and refrigerate to firm up a bit, 20 to 30 minutes.
Remove the meringues from the freezer. Use a spoon or a palette knife to spread about 1 1/2 teaspoon frosting over the bottom of each meringue. Return to the freezer frosting side up for 15 minutes to harden.
Put the chocolate in a heatproof bowl. Bring an inch or two of water to a simmer in a saucepan, put the bowl on top, and melt the chocolate, stirring occasionally, about 3 minutes ( You can use the microwave if your prefer.) Remove from the heat. The chocolate should be just warm to the touch; if it is warmer, let it cool a bit.
Dip the frosted side of each meringue in the melted chocolate so the frosting is entirely covered. Let set on a large piece of parchment paper.
Line a large container with parchment paper and arrange the meringues in it, layering them between sheets of parchment. Cover the paper and close the lid tightly. The meringues will keep in the freezer for up to a month.