Preheat oven to 175°C / 350°F. Line a muffin tin with cupcake liners. Set aside.
In a small bowl, use a wire whisk and whisk together egg whites, Part 1 milk and vanilla. Set aside.
In a medium to large mixing bowl, use another wire whisk and whisk together flour, cornstarch, sugar, baking powder and salt. Add in softened butter and Part 2 milk. Using a handheld electric mixer, beat on medium speed for 1 ½ minutes to aerate the batter. Scrape down the batter occasionally from the sides of the bowl with a spatula.
Add in the egg white mixture in 3 parts, beating well on medium speed for 30 seconds and scraping the sides of the bowl after each addition.
Fill the cupcake liners to ¾ full. You will get about 6 to 8 cupcakes, depending on the size of your cupcake liners.
Bake for 20 minutes to 25 minutes until the top is lightly golden on top and a skewer inserted into the center of the cake comes out clean. Remove the cupcakes from the muffin tin and cool completely on a wire rack before frosting.
Place finely chopped chocolate in a heatproof bowl.
Place cream in a small pot and bring to a simmer. Add the cream into the chocolate. Cover the bowl and set aside for 5 minutes.
After 5 minutes, use a wire whisk to whisk the ganache together gently, until all the chocolate has melted and the mixture is smooth. Let cool until thickened before spreading onto the cooled cupcakes. (You can also chill the ganache faster in the refrigerator, but make sure to check and stir it every 10 minutes).
1 egg white is approximately 30 grams.
A handheld mixer is used instead of a standing mixer as the quantities are small. If you doubled or tripled the quantities, feel free to use a standing mixer to make the cupcakes.