The milk is heated to about 40-50 °C, stir with a whisk cocoa and sugar (20 g), stir well until smooth, do not boil.

Separate the whites from the yolks and whip until soft peaks form, can be softer than in the photo.

Butter, sugar (200 g), vanilla sugar (I ground vanilla) and rum beat in the lush mass. One to drive the yolks.

Mix the flour, salt, baking powder and zest (I have none). With a spatula stir in flour mixture into the butter. Carefully enter the beaten egg whites dough: first stir with a spatula 1/3 of protein mass, then add the remaining proteins.

Cake pan to grease well with butter and sprinkle with flour. Slightly more than half of the dough evenly on the form. In the remaining dough with a spatula to introduce the cocoa mixture with milk. Don't worry if will seem that the dough will be thinner than whites, in the baking process all the cocoa will absorb. Spread the chocolate dough over white. With a fork or a stick to sushi to make a few "podzemnaya" movements upwards across the cupcake, slightly mixing the two tests. The surface is uniformly smooth spatula.

Bake for approximately 60 minutes at 175-180 °C. after 45-50 minutes, it is better to start to control the baking process, you can check on a dry stick. I have in this form (28 cm) cake is cooked 55 minutes at 175 °C. If you take the shape of smaller diameter (26 or 24 cm), the cupcake will turn out above, the amount of dough could save not necessarily. The surface may crack a little, but is quite acceptable.

The finished cake to turn on a wire rack and cool. Optionally, sprinkle with powdered sugar.

So the cupcake looks in the cut.