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.
Meanwhile, In a separate mixing bowl, using a whisk, sift together flour, cocoa powder, baking powder and salt. Add remaining chocolate chip, toss until coated.
In a separate bowl, whisk together sugar, eggs, corn syrup and vanilla.
Temper the wet ingredients with ¼ cup melted chocolate. Gradually whisk in the remaining melted chocolate, mix well. Set aside to cool for 5 minutes.
Once cooled, 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.