In 1-quart saucepan, heat remaining 1/2 cup chocolate chunks and the oil over low heat, stirring frequently, until smooth. Drizzle over warm brownies. Sprinkle with remaining 1/2 cup pecans; press in lightly. Cool 20 minutes. Refrigerate about 1 hour 30 minutes or until chocolate is set. For brownies, cut into 6 rows by 4 rows. If refrigerated longer, let stand at room temperature 20 minutes before serving.