Preheat oven to 350°F. Cream butter and sugar together. Add vanilla and eggs one at a time, scraping after each addition. Sift together flour, baking powder, cocoa and salt. Add dry ingredients to wet and blend well. Fold in chocolate chips. Form dough into 1” balls, dust (roll) them in the icing sugar and place on a parchment-lined cookie sheet 2”-3” apart. Bake for 12-15 minutes. Cookies will flatten and cracks will form in the icing sugar. Cool for 8-10 minutes on the pan. Remove to wire rack and cool completely. Makes about 2 dozen cookies.