Beat butter and cream cheese in a large bowl with an electric mixer on medium speed for 30 seconds. Add 1/2 cup brown sugar, vanilla, and salt. Beat until combined, scraping sides of bowl occasionally. Beat in as much flour as you can with the mixer. Stir in any remaining flour. Divide dough into three equal portions; shape each portion into a disk. Cover and chill dough in the refrigerator for 1 hour. Preheat oven to 350 F. Roll each portion of dough into a 9-inch round on a lightly floured surface. Lightly brush each round with milk. Combine nuts, 2 tablespoons brown sugar, cinnamon and nutmeg. Sprinkle nut mixture evenly over dough, leaving a 1/2-inch border. Cut each round into 12 wedges with a pizza cutter or sharp knife. Roll up each wedge, starting from the wide end. Bend ends of roll to shape it into a crescent. Place crescents 1 inch apart on ungreased cookie sheets. Bake in preheated oven for 14 to 16 minutes or until bottoms are lightly browned. Cool cookies on cookie sheets on wire racks for 2 minutes. Transfer cookies to wire racks and cool completely. If desired, sprinkle with powdered sugar before serving.