In a food processor, grind pecans, almonds and 1/4 cup confectioners sugar until the mixture is finely ground.
In medium-size bowl, on medium speed, beat butter until smooth and creamy, about 2 minutes. Add 1/2 cup confectioners sugar; beat until fluffy, about 2 minutes. Beat in nut mixture and vanilla. On low speed, beat in flour and salt. Refrigerate for 1 hour or until dough is firm enough to hold shape.
Heat oven to 350 degrees F. With floured hands, shape teaspoonfuls of dough into crescents. Place 2 inches apart on ungreased baking sheets.
Bake crescents in 350 degree oven for 12 to 14 minutes or until the cookies are lightly browned on bottoms and around edges. Transfer crescents to wire racks; let stand until warm.
Sift the remaining confectioners sugar onto plate. Roll warm cookies in sugar. Return to wire racks; let cool completely. Roll cookies again in sugar. Store in airtight container at room temperature for up to 3 weeks.
Brush sugar off one end of each crescent; dip those ends into melted chocolate, letting excess drip back into bowl. Place the cookies on waxed paper. Let stand until set. Store in airtight container at room temperature for up to 2 weeks. Makes about 5 dozen cookies.