1 cup butter, softened
1 1/2 cups white sugar
2 teaspoons vanilla extract
2 cups all-purpose flour
2/3 cup cocoa powder
3/4 teaspoon baking soda
1/4 teaspoon salt
2 cups semisweet chocolate chips
1/2 cup chopped walnuts (optional)
Preheat oven to 350 degrees F (175 degrees C).
In large bowl, beat butter, sugar, eggs, and vanilla until light and fluffy. Combine the flour, cocoa, baking soda, and salt; stir into the butter mixture until well blended. Mix in the chocolate chips and walnuts. Drop by rounded teaspoonfuls onto ungreased cookie sheets.
Bake for 8 to 10 minutes in the preheated oven, or just until set. Cool slightly on the cookie sheets before transferring to wire racks to cool completely.