1/2 cup dark cocoa (I used Hershey's Special Dark)
1 teaspoon baking soda
1 teaspoon salt
1 cup semi-sweet chocolate chips
Cream butter and sugar together, add in eggs, one at a time, beating well after each addition. Add in vanilla.
In separate bowl, stir together flour, cocoa, baking soda and salt. Add flour mixture to Butter mixture in thirds, making sure all dry ingredients are incorporated before adding more. Fold in chocolate chips.
Shape dough into a 12 x 4 inch log and place on a well greased baking pan (or use parchment paper) Bake in a preheated 350 degree oven for 30 minutes.
Remove from oven and let rest for 5 minutes. Cut loaf into 3/4 inch slices and place back on baking sheet, cut side down. Bake again for 8 minutes then turn cookies over and bake for an additional 5 minutes.
Completely cool cookies on a rack then store in an airtight container.
regular cocoa can be substituted for the dark cocoa