Preheat the oven to 325 degrees F and put mini paper liners in each cup of 2 mini muffin pans.
Put the butter and semisweet chocolate chips in a medium heatproof bowl. Microwave on high for 30 seconds. Stir with a spatula, and return to the microwave and heat on high for 30 seconds. Stir and repeat, if necessary, until mixture is smooth. Reserve.
Crack the eggs in the bowl of a stand mixer or a medium bowl with electric mixer. Beat high speed until they are pale yellow and foamy, about 3 minutes.
Stir the salt and cornstarch into the melted chocolate until they are well combined.
Pour one-third of the beaten egg mixture into the chocolate and gently stir until fully incorporated. Repeat this process two more times until all of the egg mixture is combined with the chocolate.
Fill each cup halfway with the chocolate batter.
Bake the cakes until they are set on the outside but still soft in the middle, about 8 to 10 minutes.
Cool on a wire rack to room temperature. Top each mini cake with a spoonful of Chocolate Ganache Icing. Refrigerate for 30 minutes to set the chocolate. Makes about 24 baby cakes.
To make the Chocolate Ganache Icing:
Put the chocolate chips in a heatproof bowl.
Heat the half and half in a small saucepan over medium heat just until bubbles start to form around the edges of the pan.
Pour the hot half and half over the chocolate, add a pinch of salt, and stir until smooth.
Cool for 5 minutes, and spoon over the cooled mini chocolate cakes.
Notes
High altitude directions: At elevations over 5,000 feet, reduce the oven temperature to 300 degrees F.Storage: Store any leftover mini cakes tightly wrapped in the refrigerator. For best flavor, eat within 3 days.