In a large bowl or stand mixer, beat the softened unsalted butter and cream cheese together until the mixture is smooth, creamy, and free of lumps, about 2 minutes.

Gradually add the all-purpose flour and salt to the butter mixture, mixing on low speed until a soft dough begins to hold together. Divide the dough into 3 equal portions, wrap each tightly in plastic wrap, and chill in the refrigerator for at least 1 hour until firm.

Preheat your oven to 375°F (190°C) and line two large baking sheets with parchment paper. On a lightly floured work surface, roll one portion of the chilled dough into a 10-inch circle, keeping the other portions in the refrigerator.

Cut the dough circle into 12 equal wedges using a pizza cutter or sharp knife. Place about 1/2 teaspoon of the plum butter or apricot jam on the wide outer edge of each wedge, then roll the dough tightly toward the center point to create a crescent shape.

Place the rolled cookies point-side down on the prepared baking sheets, spacing them about 1 inch apart. Bake for 12 to 15 minutes, or until the edges are lightly golden and the pastry is set.

Allow the cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely. Dust generously with powdered sugar before serving with a warm cup of tea or coffee.