- For the cake:
- 1 package (18.25 ounces) plain chocolate cake mix
- 8 tablespoons (1 stick) butter, melted
- 1 large egg
- For the filling:
- 2 cups confectioners’ sugar, sifted
- ¼ cup vegetable shortening
- 1 large pasteurized egg white (see notes below)
- ½ teaspoon pure vanilla extract
1. Make the cakes: Place a rack in the center of the oven and preheat the oven to 350°F. Set aside 2 ungreased baking sheets.
2. Place the cake mix, butter, and egg in a large mixing bowl and beat with an electric mixer on low speed until the ingredients come together in a stiff mass, 1 to 2 minutes. Form the dough into 1-inch balls with your hands or scoop the dough into balls. Place the balls of dough on baking sheets 2 inches apart.
3. Place the baking sheets in the oven and bake the cakes until they are still a little soft, 10 to 12 minutes. If your oven cannot accommodate both baking sheets on the center rack, place one on the top rack and one on the center rack and rotate them halfway through the baking time. Remove the baking sheets from the oven and let the cakes cool on them for 5 minutes. Then, using a metal spatula, transfer the cakes to wire racks to cool completely, 30 minutes longer.
4. Make the filling: Place the confectioners’ sugar, shortening, egg white, and vanilla in a medium-size mixing bowl and beat with an electric mixer on low speed until just combined, 1 minute. Spoon about 1 teaspoon onto the flat side of one cake. Top the filling with a second cake to make a sandwich. Repeat with the remaining cakes and serve.