Beat eggs with sugar, vanilla sugar and oil until creamy. Add the sparkling water, flour and baking powder and stir in. Pour the batter into 12 muffin cups.
Bake in the oven preheated to 180 ° C for about 20 minutes on the middle rack. Let cool for an hour.
For the frosting, whip soft butter with cream cheese, powdered sugar and a little grated lemon zest until creamy. Spread on the cooled muffins. Decorate with different berries according to the season and mood. Finally dust with a little icing sugar and enjoy.