In a large mixing bowl, combine the all-purpose flour and salt. Add the cold, cubed butter and use a pastry blender or your fingers to cut it in until the mixture resembles coarse crumbs.

Add the sour cream, egg yolks, and vanilla extract to the flour mixture. Mix gently until the dough just comes together, being careful not to overwork it.

Divide the dough into two equal portions, shape each into a flat disc, and wrap tightly in plastic wrap. Chill in the refrigerator for at least 30 minutes to firm up the butter and make the dough easier to roll.

Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper. On a lightly floured surface, roll one chilled dough disc into a 10-inch circle, about 1/8-inch thick.

Use a pizza cutter or sharp knife to slice the dough circle into 12 equal wedges, just like cutting a pizza. Spread about half a teaspoon of thick raspberry preserves at the wide base of each wedge.

Starting from the wide end with the jam, gently roll each wedge tightly toward the pointed tip to form a classic crescent shape. Place the rolled cookies on the prepared baking sheets with the tip tucked underneath so they don't unroll during baking.

Bake for 18 to 20 minutes, or until the rogaliki are lightly golden brown and beautifully flaky on the edges. Remove from the oven and let them cool on the baking sheet for 5 minutes before transferring to a wire rack.

Once the cookies have cooled completely to room temperature, generously dust them with powdered sugar. Serve these delicate Polish croissant cookies alongside a hot cup of tea or coffee for a delightful, comforting treat.