Preheat a waffle iron according to manufacturer's instructions.
Combine butter, sugar, vanilla sugar, and salt in a large bowl; beat with an electric mixer until smooth and creamy. Add eggs one at a time, beating well after each addition.
Combine flour and baking powder in a bowl. Beat into butter mixture 1/2 cup at a time, alternating with cream. Add a dash of sparkling water in the end to loosen up the batter.
Spray the preheated waffle iron with cooking spray. Pour batter into waffle iron, working in batches, and cook according to manufacturer's instructions, 3 to 5 minutes per waffle.
