In a bigger bowl, mix together the butter and sour cream. The butter should be at room temperature to be mixed easily.
Add the flour and baking powder to the mixture. Place the dough on a clean surface, sprinkled with flour and knead until all ingredients are well combined, forming a soft dough ball.
Let the dough rest in the refrigerator for at least 30 minutes, preferably one hour. In meantime, preheat the oven to 375F/190 C.
As before, sprinkle a clean surface with flour and roll out a half of the dough (about three millimeters thick). Return the rest of the dough to the refrigerator.
With a cookie cutter or an empty glass (diameter of about 7 cm) cut round discs from the dough. Knead the leftover of the dough again and make another batch of the discs and repeat until you have any dough left.
Top the discs with a teaspoon of your favorite jam. fold the discs over and press down the round edge firmly with your fingers. Press the edges again, this time using a fork.
Reload the cookies to a baking sheet, covered with parchment pape and bake for about 12-14 minutes at 375 F/190C until the cookies look crunchy and golden.
In the meantime; prepare another batch. When the cookies are baked, let them rest for a few minutes, then sprinkle with powdered sugar (optional) while they are still warm.
Enjoy :)