Directions

• Prepare an 9-inch diameter, 2-inch deep, preferably nonstick round cake pan by buttering it, lining the bottom with parchment, and buttering the parchment. Ready a roasting pan to serve as a water bath, and heat some water.
• Preaheat the oven to 425°F.
• Melt the chocolate and butter in the microwave on high power, stirring every 15-30 seconds. Remove when there are still a few lumps of chocoloate and stir until fully melted (see notes). Stir in espresso powder.
• Place the eggs into a mixing bowl, and set the bowl over a pan with just enough water so that the bowl doesn’t touch the water. Bring the water to a simmer (setting 4) and heat the eggs, stirring constantly to prevent curdling, until just warm to the touch, about 4½ minutes. Remove from the heat and whisk on highest speed, until triple in volume and soft peaks form when the beater is raised, about 5 minutes, gradually adding sugar in the final 30 seconds.
• Detatch the whisk from the mixer and use it to fold ½ of the eggs into the chocolate mixture by hand, until almost incorporated. Fold in the remaining eggs until just barely blended. Finish by using a rubber spatula to ensure that the heavier mixture at the bottom is incorporated. Scrape ½ of the batter into the prepared pan. Reserve 1 Tbs of the hot fudge and store it in the refrigerator. Drizzle ½ of the remaining hot fudge over the batter and top with remaining cake batter. Drizzle on the remaining hot fudge. Set the pan in the roasting pan, place the roasting pan on the pulled-out oven rack, and pour hot water into the roasting pan until the cake pan is surrounded a 1-inch pool. Slowly and carefully slide in the rack, and bake 5 minutes. Cover loosely with a piece of buttered foil and bake 10 more minutes. (The cake will look soft and unset, but this is as it should be.)
• Let the cake cool on a rack, 45 minutes. Cover with plastic wrap and refrigerate until very firm, about 3 hours or overnight.
• To unmold, have ready a serving plate and a flat plate at least 9 inches in diameter, and lay a tea towel out flat on the countertop. Fill the sink with the hottest water your tap will produce, to a depth that is close to but less than the height of the cake pan. Remove the plastic wrap from the cake, but lay it out flat so you can reuse it. Carefully dip the cake pan into the water, covering as much of the side of the pan as you dare. Hold for ten very long seconds. Carefully remove, and set the pan on the towel. Run a thin metal spatula around the interior perimeter of the pan. (Don’t use a knife; it will scratch your pan.)
• Dip the pan into the water again, this time for 30 seconds. Remove to the towel, and place the plastic wrap loosely over it. Place the flat plate on top of the plastic. Pick up the pan, plastic, and plate as if it were one thing, invert it, and place it back onto the towel. Slap the pan rather firmly with both hands, to try to shock the cake out of the pan. (Don’t worry; the cake is pretty sturdy when refrigerated.)
• Repeat Step 8 as necessary until the cake unmolds.
• Remove the parchment. Holding the flat plate in your nondominant hand, invert the serving plate and place it atop the cake without compressing the cake. (This is easier if your “cake plate” is a cake stand.) Invert everything, set it on the countertop, and remove the flat plate and plastic. If there are mars or discolorations in on the top of the cake, use the reserved, reheated hot fudge to touch them up.
• Although it can be served immediately, it’s best at room temperature, which takes at least 30 minutes for pre-cut slices. (Unless you intend decorate and present it whole, I suggest cutting cold slices, letting them come to room temperature, and then garnishing them just before serving.)
• Garnish with Whiskeyed Cherries, vanilla ice cream, and whipped cream.