For the truffle eggs:
For the cake:
For the ganache:
For the nests:
To make the truffle eggs, place the bittersweet chocolate in a heatproof bowl. Bring the cream to a simmer and pour over the chopped chocolate. Let sit about 1 minute, then whisk to combine. If there are remaining small bits of chocolate that have not melted, microwave the mixture in 15 second intervals until the chocolate is completely melted and a thick ganache has formed. Whisk in the butter. Cover the bowl and chill in the refrigerator until firm, at least 2 hours.
Scoop out small portions of the ganache and mold into small egg shapes. Place on a parchment lined plate and chill in the freezer, at least 1 hour. When you are ready to dip the truffles, melt the white chocolate or candy melts until smooth. If desired, tint with candy coloring. Dip the truffle centers, coating completely and shaking gently to remove the excess. Return to the parchment-lined plate. Chill the coated truffles in the refrigerator until completely set. Use a clean paintbrush to apply pearl or luster dust, if desired.
To make the chocolate cakes, preheat the oven to 350˚ F. Line the bottoms of 4 mini-springform pans with parchment paper. Grease the sides of the pans and dust with cocoa powder. Melt the butter in a medium saucepan over medium heat. Add the cocoa powder, espresso powder, and water, and whisk until smooth. Whisk in the sugar. Remove from the heat. Whisk in the egg, buttermilk and vanilla. Add in the flour, baking soda and salt, and whisk just until incorporated. Divide the batter between the prepared pans. Place the pans on a baking sheet. Bake for 22-26 minutes or until a toothpick inserted in the center comes out clean, rotating the pan halfway through baking. Transfer the pans to a wire rack and allow to cool completely. Run a thin knife around the edge of the pan before carefully removing the sides of the springforms. Remove the cakes from the bottoms of the pans and peel away the parchment paper. Level the tops of the cakes with a sharp knife.
To make the ganache, place the chocolate in a liquid measuring cup or bowl with a spout. Bring the cream to a simmer. Pour over the chocolate and let stand 1-2 minutes. Whisk together until a thick, smooth ganache forms. Whisk in the corn syrup.
Place the cooled cakes on a wire rack set over a baking sheet. Pour the warm ganache over the cakes to coat smoothly. Use a small offset spatula to help cover any naked spots. Let stand until the ganache is completely set.
Sprinkle chocolate shavings around the perimeter of the cakes to look like a nest. Place the truffle eggs in the centers of the nests.