Melt butter with chocolate in saucepan over low heat; cool.
Add sugar , egg, vanilla and salt; mix thoroughly.
Stir in flour.
Shape into balls, using a teaspoonful for each.
Place on ungreased baking sheet.
Bake at 375 for 8 to 10 min. or until delicately browned.
While warm, roll in confectioners'sugar.