Make the Chocolate Bundt Cakes Preheat the oven to 350°F and position an oven rack in the center. Prepare the pan by buttering or oiling (with cooking spray) each mold thoroughly, then dusting with flour or fine dry bread crumbs and tapping out the excess.
Cream the butter and sugar: Place the butter and sugar in the bowl of the stand mixer and beat on medium-high until light-almost white-in color, 4 to 5 minutes. You can also use a hand mixer and a medium bowl, although you may need to beat the mixture a little longer to achieve the same results. Scrape down the bowl with the spatula.
Add the eggs: In the small bowl, stir together the water and espresso powder until smooth. Crack the eggs into the bowl and beat to blend. With the mixer running on medium, add the eggs to the butter mixture about 1 tablespoon at a time, allowing each addition to completely blend in before adding the next. About halfway through, turn off the mixer and scrape down the bowl, then continue adding the eggs. Scrape down the bowl again.
Add the dry and wet ingredients alternately: With the fine-mesh strainer, sift the flour, cocoa powder, baking powder, and salt into the medium bowl and whisk to blend. With the mixer running on the lowest speed, add the flour mixture and the buttermilk alternately, beginning with one-third of the flour mixture and half of the buttermilk; repeat, then finish with flour mixture. Scrape down the bowl and finish blending the batter by hand, if necessary.
Bake the cakes: Spoon 3 tablespoons batter in each Bundt mold. Bake for 13 to 15 minutes, until firm to the touch and a toothpick inserted into the center comes out clean. Do not overbake, as these small cakes dry out quickly. Transfer to a rack and cool for 10 minutes, then turn the cakes out while they are still warm. Rinse the baking pan under cold water until cool, dry thoroughly, prepare again and bake the remaining batter. Fill any unused molds halfway with water so the cakes bake evenly.
Storing: The cakes can be made several days ahead and kept at room temperature, wrapped in plastic wrap. Or double-wrap, put in a resealable plastic freezer bag, and freeze for up to 8 weeks.
Make the Dark Chocolate Ganache Place the chocolate in the medium bowl. Heat the cream in the small saucepan over medium heat until it begins to boil. Immediately pour the cream over the chocolate. Let the mixture sit for 1 minute, then gently whisk until the ganache is completely smooth and blended. If you are using a high-percentage chocolate and the mixture looks broken or curdled at this point, stir in an extra tablespoon or two of cream, just until the mixture smooths out again. Use as directed. To use as frosting: Let the ganache cool for 1 hour, then cover with plastic wrap and set aside to finish cooling at room temperature until it has the consistency of frosting, 8 to 10 hours. If you make it the night before, it will be the perfect texture for frosting cakes and cupcakes in the morning. To use as a glaze: Set the ganache aside until it has cooled to the consistency of pourable honey, 15 to 20 minutes. Pour the ganache over the cake. You can also dip the tops of cupcakes, cream puffs, or éclairs into the ganache for a quick-and-easy icing. To use as a sauce: Spoon the ganache onto the dessert plates or over ice cream while still warm. If it has cooled and is too thick, heat gently over a double boiler until warm and fluid, or simply add additional cream (or water) until the desired sauce consistency is reached.
Make the Spun Sugar Makes enough to drape and top a 9-inch cake, make 8 individual (3-inch) nests or 12 small (1-inch) nests, or create lots of drizzled decorations.
Cover the floor and cabinets with parchment paper or newspaper in a 3-foot area along the counter where you will be working. Line the baking sheet with parchment paper or a silicone mat. Lightly oil the wooden spoons or dowels and arrange them on your work surface so that their handles protrude from the edge of the surface by 7 or 8 inches. Position them 6 to 8 inches apart and set a heavy saucepan or pasta pot on them to hold them in place.
Fill the medium bowl halfway with ice and water and set it aside. Pour the water into the small saucepan. Sprinkle the sugar over the top 2 to 3 tablespoons at a time, allowing each addition to moisten before adding the next. Add the cream of tartar or corn syrup. Set the pan over medium-low heat and stir until the sugar is dissolved and the liquid is clear.
Increase the heat to high and boil rapidly, swirling the pan occasionally so that the sugar cooks evenly (do not stir). Cook until the sugar turns amber. Test the color by dipping a clean spoon into the caramel and dripping a bit on a white plate. This is one of the few instances where you do not want a dark golden brown color, so keep it light.
Immediately remove the caramel from the heat and set the bottom of the saucepan in the bowl of ice water. This will stop the caramel from cooking-and coloring-any further. Hold it in the ice water for about 5 seconds; then remove, dry the bottom of the pan, and set on the trivet or on a folded kitchen towel.
Let the caramel cool, testing it every minute or so, until it falls off the ends of the whisk in thin streams rather than drops. Dip the ends of the whisk into the caramel and fling it quickly back and forth across the top of the spoon handles. The caramel should form thin, gossamer threads between the spoons. Repeat 2 or 3 times, then gather the spun sugar with your hands, pull it off the dowels, and shape it as desired, working quickly as the spun sugar becomes quite brittle as it cools. Set the shape on the prepared baking sheet. Repeat until you have used all the sugar or until you have enough spun sugar for your needs. If the caramel cools and becomes too thick to use, simply reheat over low heat until fluid again (don't boil or the caramel will darken too much).
Drape the spun sugar around a cake, on top of a tart, around a cream puff, or stack layer after layer of it to create a huge beehive for a dramatic presentation. Spun sugar is at its best the same day it is made, so serve the sugar or decorate with it within a couple of hours.
