In mixing bowl, stir together flour, cornstarch, baking powder, salt, sugars and cocoa.
Add vegetable oil, and mix thoroughly. (Mixture in bowl should look a bit crumbly).
Add butter, eggs, water and add ins. Stir until completely mixed and dough holds together.
Forms balls about 1-1/2 inches in diameter and place on prepared cookies sheets. Cookies will flatten out a bit while baking, but will not spread a lot.
Bake for 10-12 minutes. Remove from pan and cool on wire rack.