Heat oven to 350 degrees Fahrenheit. Stir together flour, cocoa, baking soda, and salt. In large bowl, beat butter and sugar with electric mixer until light and fluffy, aprox.20 minutes. Add eggs and vanilla; beat well. Gradually add flour mixture, beat well. Stir in chocolate chips. Drop by rounded teaspoons onto ungreased cookie sheet. Bake 8-9 minutes. (Do not over bake; cookies will be soft. They will puff up while baking and flatten while cooling.) Cool slightly; remove from cookie sheet to wire rack. Cool completely.
Makes about 4-1/2 dozens cookies.
VARIATION Omit the chocolate chips for peanut butter chips
High Altitude Direction
Increase flour to 2 cups plus 2 Tablespoons
Decrease baking soda to 1/8 teaspoon
Decrease sugar to 1 2/3 cups
Add 2 teaspoons water with flour mixture
Bake 350 degrees Fahrenheit, 7-8 minutes
Yield increases to about 6 dozen