Hershey's Doubly Chocolate Brownies

3/4 cup Hershey's Cocoa
1/2 teaspoon baking soda
2/3 cup butter or margarine, melted and divided
1/2 cup boiling water
2 cup granulated sugar
2 eggs
1 1/3 cups all-purpose flour
1 teaspoon vanilla extract
1/4 teaspoon salt
1/2 cup coarsely chopped nuts (optional)
1 3/4 cups (10 ounce package) Hershey's Premium
    Semi-Sweet Chocolate Chunks

Preheat oven to 350 degrees F. Grease a 13 x 9-inch baking pan. 

In large bowl, stir together cocoa and baking soda; blend in 1/3 cup of the butter. Add boiling water; stir until mixture thickens. Stir in sugar, eggs and remaining 1/3 cup butter; stir until smooth. Add flour, vanilla extract and salt; blend well. Stir in nuts, if desired, and chocolate chunks. Pour into prepared pan. Bake for 35 to 40 minutes or until brownies begin to pull away from sides of pan.

Cool completely in pan or on wire rack. Cut into squares.

Yields about 36 brownies.