For the wind baking, in a very clean bowl, beat the egg whites and salt with a mixer until the mixture is thick and creamy. While continuing to whisk, sift in the granulated sugar with the vanilla sugar, continuing to whisk until the beaten egg whites are very firm and dull glossy. Then sift the powdered sugar over it and fold it in carefully.
Preheat the oven to 100 ° Celsius. Fill the mixture into a piping bag and pipe rings onto a baking tray with baking paper. Sprinkle with colored sprinkles if desired.
Dry the wind bakery for about 3 hours in the oven rather than bake. In between, keep opening the oven to let the moisture escape. At the end of the baking time, allow the wind baked goods to cool with the oven door open and the oven turned off.