Ultimate Double Chocolate Brownies

This recipe took grand prize in my mom's favourite magazine.

Ingredients:
3\4 cup baking cocoa
1\2 teaspoon baking soda
2\3 cup butter or margarine,melted,divided
1\2 cup boiling water
2 cups sugar
2 eggs
1-1\3 cups all-purpose flour
1 teaspoon vanilla extract
1\4 teaspoon salt
1\2 cup coarsely chopped pecans (optional)
2 cups (12 ounces) semisweet chocolate chunks

In a large bowl, combine cocoa and baking soda; blend in 1\3 cup melted butter. Add boiling water;stir until well blended. Stir in sugar,eggs and remaining butter. Add flour,vanilla and salt. Stir in the pecans and chocolate chunks. Pour into a greased 13-in. by 9-in. baking-pan. Bake at 350 for 35-40 minutes or until brownies begin to pull away from sides of pan. Cool.