Heat oven to 350 degrees. Line two baking sheets with parchment paper, and set aside. In the bowl of an electric mixer fitted with the paddle attachment, combine butter and sugar.
In a large bowl, combine flour, salt, and cocoa powder. Add flour mixture to butter mixture; mix on low speed just until a stiff dough forms, about 2 minutes. Transfer dough to a piece of plastic wrap, wrap tightly, and chill until firm, about 30 minutes.
Place chocolate, heavy cream, and espresso powder in a medium heatproof bowl. Place the bowl over a pan of gently simmering water, stirring occasionally, until chocolate has melted. Remove bowl from heat, and set the chocolate ganache aside to cool, stirring occasionally.
On a lightly floured surface, roll out chilled dough to a 1/4-inch thickness. Using a 2 1/4-inch-round cookie cutter, cut out 24 cookies; place them on lined baking sheets. Chill cookies until firm, about 20 minutes.
Bake cookies until set, about 14 minutes. Transfer to a wire rack to cool completely.
For colored coconut, combine a few drops of food coloring with 3 tablespoons water in a medium bowl. Stir in coconut; mix until evenly colored. Spread on an ungreased baking sheet; bake just until dry, about 12 minutes, being careful not to brown. Let coconut cool; transfer to a small bowl.
When the ganache has cooled to room temperature, whisk until it becomes stiff enough to pipe. Transfer ganache to a pastry bag fitted with a 3/8-inch-round tip, and pipe around perimeters of cookies. Dip each cookie, ganache-side down, into plain or colored coconut. Fill "nests" with candy-coated chocolate eggs, 2 or 3 eggs per nest.
Store cookies in an airtight container, refrigerated, up to 3 days.