Combine sugar and butter and cream together thoroughly. Add eggs and vanilla.
Combine together flour, baking soda & powder, cornstarch, and salt. Gently whisk this together and then add into wet ingredients. Mix.
Add semi-sweet and dark chocolate. Mix.
Line cookie sheet with parchment paper, create tablespoon sized balls of dough (or larger) (smooshing dough and adding more chips as you see fit.) Leave 3-4" for spreading.
Oven 350 F for 13-16 min or until edges are lightly golden brown.