Preheat oven to 325 °F. Grease a 9-inch square baking pan. In a small bowl, mix together flour and baking soda; set aside. In a small saucepan, combine butter, sugar and water. Bring to a boil over medium heat; remove immediately from heat. Stir in 1 cup of chocolate morsels and vanilla extract until chocolate is melt and mixture is smooth. Transfer mixture to a medium bowl. Cool completely. Stir in eggs, 1 at a time, beating well after each addition. Gradually stir in flour mixture until smooth. Stir in remaining chocolate morsels and nuts into batter. Pour batter into prepared pan. Bake 30 to 35 minutes, until a toothpick inserted in center comes out clean. Transfer pan to a wire rack to cool completely. Cut into squares.