PREHEAT oven to 350º F. Grease a 13 x 9-inch baking pan.
MELT 1 cup chunks and butter in large, heavy-duty saucepan over low heat, stirring constantly, until smooth. Remove from heat; stir in eggs. Add flour, sugar, vanilla extract and baking soda; stir well.
SPREAD batter into prepared baking pan; sprinkle with remaining chunks and nuts.
BAKE for 20 to 25 minutes or until wooden pick inserted in center comes out slightly sticky.
MICROWAVE caramels and milk in small, microwave-safe bowl on HIGH (100%) power for 1 minute; stir. Microwave at additional 10- to 20-second intervals; stir until smooth. Drizzle over warm brownies. Cool in pan on wire rack. Cut into bars.