Make the dark chocolate truffle hearts. Place 8 ounces chopped semisweet chocolate in a small bowl. Heat 3/4 cup heavy cream in a small saucepan over a medium heat. Bring to a boil. Pour the boiling cream over the chopped chocolate. Set aside for 5 minutes before stirring with a whisk until smooth. Pour the mixture (called ganache) onto a nonstick baking sheet and use a rubber spatula to spread the ganache in a smooth, even layer to within about an inch of the inside edges of the pan. Place the ganache in the freezer for 15 minutes, or in the refrigerator for 30 minutes, until firm to the touch. Line a 10 to 12-inch dinner plate with parchment paper or waxed paper. Remove the firm ganache from the freezer or the refrigerator. Portion 12 heaping tablespoons (a bit more than an ounce each) of ganache onto the paper. Wearing a pair of disposable vinyl (or latex) gloves, individually roll each portion of ganache in your palms in a circular motion, using just enough gentle pressure to form a smooth orb. This is a traditional truffle. You should refrain from indulging in them since absence of a truffle in a cake will make the heart grow darker. Return each formed truffle onto the paper lined plate, and place in the freezer while preparing the cake batter.

Make the chocolate cocoa cakes. Preheat the oven to 325 degrees F. Lightly coat the inside of each individual nonstick muffin cup with the 2 teaspoons melted butter. Set aside until needed. In a sifter, combine 2/3 cup all-purpose flour and a 1/2 cup cocoa powder. Sift onto a large piece of parchment paper (or waxed paper) and set aside until needed. Melt 8 ounces chopped semisweet chocolate and 5 ounces butter in the top half of a double boiler over medium-low heat. Use a rubber spatula to stir the chocolate and butter until completely melted and smooth, about 6 to 7 minutes. Remove from the heat and set aside at room temperature until needed. The chocolate and butter may also be melted in a medium glass bowl in a microwave oven set at medium power for 2 minutes. After removing the chocolate and butter from the microwave oven, use a rubber spatula to stir until smooth.

Place 3 eggs, 2 egg yolks, and 1/2 cup sugar in the bowl of an electric mixer fitted with a paddle. Beat on a medium-high speed for 2 minutes until the mixture is slightly frothy. Add the melted chocolate and butter and mix on low speed to combine, about 15 seconds. Continue to operate the mixer on low while gradually adding the sifted dry ingredients. Once all the dry ingredients have been incorporated, stop the mixer and scrape down the sides of the bowl. Add 1 teaspoon vanilla extract and mix on medium to combine, about 15 seconds.

Remove the bowl from the mixer and use a rubber spatula to finish mixing the batter until thoroughly combined. Portion 3 heaping tablespoons (about 2 1/2 ounces) of the cake batter into each individual muffin cup. Place the muffin tin on the center rack of the preheated oven. Bake for 5 minutes. Remove the truffles from the freezer.

Remove the muffin tin from the oven, and moving quickly, place a single frozen truffle in the center of each portion of cake batter, pressing each truffle about halfway down into the batter. Immediately return the muffin tin to the center rack of the oven and bake until a toothpick inserted into the cake (not the truffle) comes out clean, about 17 to 18 minutes. Remove the cakes from the oven and cool at room temperature for 20 minutes. To remove the cakes from the muffin cups, hold the top edges of the baked batter part of a cake, and give each cake a slight twist to loosen it from the inside cup. Then insert the pointed tip of a knife into a top outside edge of a cake and loosen it so that you can gently pull each baked cake out of each cup. Serve immediately while still warm.

After the Chocolate Heart of Darkness cakes have cooled to room temperature, you may keep them covered with plastic wrap for up to 24 hours at room temperature, or in the refrigerator for 3 to 4 days. The cakes may be rewarmed in a microwave oven, and they are extraordinary. Make sure the cakes are at room temperature, then heat them 1 or 2 at a time for 30 to 40 seconds in a microwave oven set on defrost power. Instead of drying out, the cake will be warm and moist, and the truffle center will be a hot ooze of ecstasy. For extra indulgence, serve the warm Chocolate Heart of Darkness cakes with white chocolate ice cream or unsweetened whipped cream. For me, a glass (forget the golden goblet) of Warre's 1985 Porto will have a salubrious effect.