Melt 1 cup morsels in small, heavy saucepan over lowest possible heat. When morsels begin to melt, remove from heat; stir. Return to heat for a few seconds at a time, stirring until smooth. Cool to room temperature.
Combine flour, baking powder and salt in small bowl. Beat together granulated sugar, margarine and vanilla in large mixer bowl. Beat in melted chocolate; beat in egg whites. Gradually beat in flour mixture alternately with water. Stir in remaining morsels. Cover; chill until firm.
Shape dough into 1-1/2 inch balls; roll in powdered sugar to coat generously. Place on greased baking sheets.
Bake in preheated 350F oven for 10 to 15 minutes or until sides are set but centers are still slightly soft. Cool for 2 minutes; remove to wire racks to cool completely. Makes about 3 dozen cookies.