Sift flour, baking powder, and salt together onto a sheet of waxed paper.
Beat 1/4 cup white sugar, butter, and cream cheese together in a bowl with an electric mixer until creamy. Beat in egg yolk and vanilla.
Stir flour mixture into butter mixture until dough is just combined. Divide dough into 3 equal portions; shape each portion into a disk, wrap disks in plastic wrap, and refrigerate for at least 4 hours or overnight.
Beat egg white in a bowl with an electric mixture until frothy. Mix walnuts and 1/2 cup white sugar into egg white.
Preheat oven to 350 degrees F (175 degrees C).
Remove dough from plastic wrap and roll each disk out into a 7-inch circle. Spread 1/3 the egg white mixture onto each dough circle, leaving a 1/4-inch border around the edge of each circle. Cut each circle into 12 wedges. Roll up each wedge from the edge to the point and place, point-side down, on a baking sheet.
Bake in the preheated oven until lightly browned, 12 to 14 minutes. Transfer to wire racks to cool and dust with confectioners' sugar.
Dough must be well chilled; remember to allow enough time to chill.