For the Dough: 100 g (½ cup) soft unsalted butter, at room temperature

100 g (½ cup) granulated sugar

1 large egg

100 g (½ cup) sour cream

350 g (about 2¾ cups) all-purpose flour

1 tsp baking powder

1 tsp vanillin or vanilla extract

Pinch of salt

For the Filling: 300 g (about 1¼ cups) cottage cheese

30 g (3 Tbsp) cornstarch

3 Tbsp powdered sugar

1 egg white (reserve the yolk for brushing)

Zest of ½ orange (optional)

For Finishing: 200 g (about 1½ cups) extra flour for dusting

Egg yolk mixed with 1 Tbsp milk, for wash

Extra powdered sugar, for dusting