Make the cakes:
1. Heat the oven to 350 degrees F (175 degrees C). Butter and flour the molds.
2. Beat the butter and sugars in the bowl of a stand mixer until fluffy, about 5 minutes. Meanwhile, sift the flour, cocoa, baking soda, and salt into a medium bowl and set aside. Add the egg and then the yolk to the butter and sugar mixture, scraping the bowl after each addition. Add the sour cream and chocolate extract, if using, and mix until combined. Alternate adding the dry ingredients and the instant coffee mixture in 3 additions, beginning and ending with the dry ingredients.
3. Divide the batter evenly among the molds, filling them almost to the top. Bake until a toothpick inserted in the center comes out clean, 20 to 25 minutes. Set the molds on a wire rack and let cool for 5 minutes. Run the tip of a knife around the rim of each cake and lift out. Place the cakes on the wire rack to cool completely.
Make the filling and frosting:
4. While the cakes cool, in a small, heavy saucepan over medium heat, bring the sugar and water to a boil. Cover and cook for 3 minutes. Uncover and continue to cook until the syrup reaches the soft-ball stage or registers 235 degrees F to 240 degrees F (112 degrees C to 115 degrees C) on a candy thermometer, about 3 minutes.
5. Meanwhile, using a stand mixer, beat the egg whites on high speed until frothy. Add the salt and beat until the whites are glossy and hold soft peaks. When the syrup is at the desired temperature, carefully pour it in a very thin stream down the side of the bowl into the egg whites with the beater still on high speed. Continue to beat until the mixture cools, 8 to 10 minutes. Beat in the vanilla. Scoop out and reserve about 3/4 cup of the meringue. Add three drops of the red food coloring to the remaining meringue in the bowl of the stand mixer and mix until combined.
6. Place the coconut in a food processor fitted with a metal blade, add three drops of food coloring, and pulse 15 times. Turn the coconut into a large bowl.
Assemble the sno balls:
7. Using a serrated knife, carefully slice off the top third of each cake, keeping each top alongside its cake. Pinch about a tablespoon and a half of cake from the inside center of each cake and set aside for nibbling. Fill the hole with a dollop of the reserved white meringue and replace the top. Thickly frost the top of the cakes with the pink meringue. Then generously sprinkle each cake with coconut until completely covered. Tamp down gently on the coconut to maintain the domed shape. Serve at once.
Recipe used with permission. Homemade Sno Balls Recipe © 2004 David Leite. Photo © 2004 Robert Olding. All rights reserved.