Preheat the oven to 350°F. Spray a 13 x 9 inch pan with baking spray. Set aside.
In a double boiler or in a heat proof bowl over 1 inch simmering water, melt together butter and 1 cup chocolate chips. Melt until completely smooth.
In a separate bowl, stir together sugar, eggs, corn syrup and vanilla by hand.
Temper the sugar-egg mixture with 1/4 cup melted chocolate. Slowly add the remaining melted chocolate, mix well. Set aside to cool for 5 minutes.
Meanwhile, In a separate mixing bowl, using a whisk sift together flour, cocoa powder, baking soda and salt. Add remaining chocolate chip, toss until coated.
Add chocolate mixture to the sifted dry ingredients. Mix by hand until fully moistened.
Spread evenly in pan. Place into the oven to bake for 25-30 minutes or until a toothpick inserted into the center shows moist crumbs. Do not over bake.
Cool in the pan on a cooling rack for at least 2 hours before cutting Store in an airtight container at room temperature.
You can bake these brownies in a 13 x 9 inch or two 9 x 9 inch pans, if desired. When baked in a 13 x 9 inch pan the center may be more gooey. Bake for 25 -27 minutes.
If you over bake these brownies, they will be dry. When testing the center, look for moist crumbs not a clean toothpick. When you see moist crumbs, they're ready to remove from the oven.
If making in cup cake form, spritz the cup cake liners with cooking spray before filling for easy release. Bake for 22-25 minutes until a toothpick inserted into the center comes back with moist crumbs. Adjust the baking time according to your oven, if needed.