Place oil and water in a small saucepan and bring to boil over medium heat.
As soon as the mixture comes to a boil, put it aside to cool for 10 minutes in a different bowl.
Preheat over to 360F.
Using a stand mixer or hand mixer, combine flour and baking powder in a large mixing bowl.
Slowly pour the water and oil mixture to the flour mixture.
Mix all the ingredients together until well combined.
Remove the dough from the bowl and knead by hand for 1-2 minutes. If the dough feels too soft, add a bit more flour.
Divide the dough in to two balls and work one half of the dough at a time.
Sprinkle flour over a clean work surface and using a rolling pin, roll out the dough until it is thin (about 5mm high) and even. Typically the thinner the dough the better for this type of cookie.
Using the rim of a glass to cut circle shapes into the dough. Dip the rim in flour to prevent the dough from sticking.
Add ½ tsp of jam to the middle of each circle.
Fold one side over to make a ½ circle shape.
Use a fork and gently presss along the sides to seal the edges leaving light indents around the half circle.
Move the cookies on to a parchment lined baking sheet and bake in the oven for 15 minutes.
Remove from oven and after 5 minutes transfer them to a cooling rack.
Combine a small bowl full of icing and vanilla sugar.
While skoljkice cookies are still warm, dip them into the sugar mixture to coat and put aside to cool completely.