Beat the butter with the sugar until creamy.

Add yolks, zest and whisk. Add half of the flour, salt, soda, baking powder and mix well. Add sour cream and stir.

Add remaining flour and knead the dough. Chocolate grind to a state of crumbs, add to the batter and mix.

Spread the dough on the molds.

Bake at 180 degrees in preheated oven for about 25-30 minutes. After the cool.

While our cupcakes in the oven, do some cooking cream. Water and 50 g of sugar to pour into a ladle. The remaining sugar vzbit proteins to a light foam. Bring to a boil over medium heat the mixture in the ladle and cook until it reaches 116 to 118 degrees (I used a cooking thermometer). Continue to whisk the egg whites and pour a thin stream of hot syrup. Beat until hard peaks to room temperature, about 5 minutes.

To start add the butter 2-3 cubes at a time (after having cut it into small pieces). The cream should be soft and homogeneous.

Add color and zest to the cream, mix well.

Using a pastry bag to decorate cupcakes with cream.