Preheat the oven to 320 degrees Fahrenheit (160 degrees Celsius).
Chop the chocolate into small pieces.
Place the cupcake forms in the cupcake baking plate.
Sieve the cornstarch, flour, salt, and baking powder in a large bowl.
In a second bowl mix the egg whites with the mixer until they are stiff ( if you hold the bowl upside down, the egg whites may not fall out).
In a third bowl mix the butter until it is pale yellow.
Then mix in the sugar and vanilla extract and mix for another 3 minutes.
Add ⅓ of the flour mixture, mix it through, pour half of the milk, mix further.
Add again ⅓rd part of the flour mixture, then the remainder of the milk, and finally the rest of the flour. Meanwhile, keep on mixing at low speed.
Mix with the spatula the chocolate pieces through the batter.
Add a quarter of the egg white and stir with the spatula through the batter.
Once incorporated you carefully add the rest of the egg whites and mix gently through with the spatula.
Spoon each muffin form almost full with batter and put in the oven.
Bake the cupcakes for 24 minutes (or until done). You can check that by pricking with a satay pricker in the middle of a cupcake. If it comes out dry, the cupcakes are done. Otherwise, you extend the baking time by 2 minutes.
Remove from the oven and put the cupcakes on a wire rack to cool.
If you still have some batter refill the baking forms and bake in the oven until all the batter is used.
In this recipe, cornstarch is used which is mixed with the flour. Therefore the cake becomes soft and fluffy.
The baking powder is used to rise you get beautiful cupcakes. Use baking powder and not baking soda. Baking powder starts working when adding liquid. When using baking soda you also need something acidic.
Use all ingredients at room temperature, that way the cupcakes will become airier.
Substitute cornstarch, flour, and baking powder with 450 grams cake flour
You can substitute milk chocolate with dark or white chocolate chips.