1. Heat oven to 350°F.
2. Beat butter and granulated sugar in large bowl until light and fluffy. Add eggs and vanilla; beat well. Stir together flour, cocoa, baking powder and salt. Gradually beat into butter mixture. Stir in chocolate chips.
3. Roll dough into 1-inch balls. Place on ungreased cookie sheet. Flatten balls with tines of fork. Flatten again in opposite direction, forming crisscross marks.
4. Bake 8 to 9 minutes or just until cookies are set. (Do not overbake; cookies will be soft.) Cool slightly; remove from cookie sheet to wire rack. Cool completely. Makes about 6 dozen cookies.