Preheat oven to 350 degrees. In a large bowl or large bowl of an electric mixer, mix butter, sugar, melted chocolate and vanilla until blended. Add eggs, one at a time, mixing until blended between additions. Into a separate bowl, sift the flour, baking powder and salt. Stir dry ingredients into the batter. Cover; chill dough 30 minutes. Roll dough into 1-inch balls. Roll balls in powdered sugar and place 2 inches apart on an ungreased baking sheet. Bake in 350-degree oven for 12 to 15 minutes, or until edges are set. Remove from oven and immediately press in the nonpareils. Let stand 1 minute, then remove from pan. Makes 5 dozen. ----