Prepare the Dough
In a large bowl, mix the flour, salt, baking powder, and vanilla sugar.
Add cold butter and rub it into the dry ingredients until the mixture resembles coarse crumbs.
Stir in the sour cream and egg, then knead until a smooth dough forms. Cover and refrigerate for 15 minutes.
Make the Orange Filling
In a saucepan, combine the chopped oranges, sugar, and cornstarch.
Cook over medium heat, stirring frequently, until the mixture thickens into a jam-like consistency. Let it cool.
Shape and Bake
Preheat the oven to 180°C (350°F).
Roll out the dough on a floured surface and cut into small circles or shapes of your choice.
Place a small amount of filling in the center of each, fold, and seal the edges.
Arrange on a lined baking sheet and bake for 12-15 minutes, or until golden.
Cool and Serve
Let the cookies cool slightly before serving. Dust with powdered sugar for extra sweetness if desired.