Mix 1 cup sugar, eggs, oil, and vanilla together in a large bowl until well blended. Stir in melted margarine. Stir in flour, cocoa, baking powder, and salt. Mix until well blended. Stir in white chocolate chips. Mix until well blended.
Cover and chill until dough is firm enough to shape into balls, about 1 hour.
Meanwhile, preheat the oven to 300 degrees F (150 degrees C).
Roll dough into 1 1/2-inch balls. Roll balls in remaining 3 tablespoons sugar. Place 2 inches apart on ungreased cookie sheets.
Bake in the preheated oven until crackled on top and slightly firm to the touch, about 20 minutes. Cool on the baking sheet for 1 minute before removing to a wire rack to cool completely.