For the blueberry chocolate cupcakes, preheat the oven to 160°C. All ingredients should be at room temperature. For the sponges, separate the eggs. Beat egg whites with salt and 40 g sugar until stiff peaks form, refrigerate.
Separately, beat the butter with 60 g sugar and vanilla sugar until light and fluffy. Beat in the egg yolks one by one, beating for about 1-2 minutes after each yolk. Stir in the flour with the baking powder and chocolate and gently fold in the snow. Pour into a muffin tin lined with paper cups with 12 wells and place 5-6 blueberries, dabbed briefly in flour beforehand, on top of each batter. Bake for 35-40 minutes. Allow the sponges to cool.
For the blueberry puree, cook the blueberries with the preserving sugar for about 10 minutes on low heat and then refrigerate overnight. For the topping, briefly mix all the ingredients in a bowl with a spoon and then blend with a blender on high speed for about 15 seconds. Pour into a piping bag and pipe onto the sponges in a circle. Decorate the blueberry chocolate cupcakes with one blueberry each and sprinkle some sugar pearls on top.