Preheat oven to 350 degrees. Prepare a 9x13 tray with cooking spray.

In the bowl of a stand mixer or a large bowl with a hand mixer, cream together butter and sugars. Cream for at least 3 minutes, until mixture is very light and fluffy. Add eggs, on at a time, mixing well after each addition. Add vanilla.

Add flour, cocoa powder, and salt and mix until combined. Stir in chocolate chips or chunk

Pour mixture into prepared 9x13 pan and spread evenly.

Bake for 30-36 minutes. Don't over bake! Brownies are done when the top is matte and not wet looking, and a toothpick inserted in the middle comes out with wet crumbs; not liquid.