In a bowl, beat together the Cream Cheese and softened Unsalted Butter until smooth and creamy.
Stir in the All-Purpose Flour and a pinch of Salt until the mixture forms a soft, slightly crumbly dough; gently knead it a few times just to bring it together.
Shape the dough into a disk, wrap it in plastic, and chill for at least 1 hour to firm up.
Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
On a lightly floured surface, roll the chilled dough to about 1/8-inch thickness and cut into roughly 3-inch squares.
Place a small spoonful of Fruit Preserves in the center of each square.
Fold opposite corners of each square toward the center and gently press to seal, forming the classic kolaczki shape.
Brush the tops with beaten Egg White to give them a light sheen and help them brown evenly.
Bake the pastries for 12–15 minutes, or until the edges are just golden.
Allow the kolaczki to cool on a wire rack, then dust with sifted Powdered Sugar before serving.
