Mix rosemary, thyme, and garlic powder in small bowl. Reserve 1/2 tsp. Heat 1 tsp. butter in large saucepan on medium heat. Add mushrooms, carrots, and remaining seasoning mixture; cook and stir 3 minutes. Remove from saucepan. Set aside. Melt remaining 3 tsp. butter in saucepan on medium heat, stirring to release browned bits from bottom of skillet. Sprinkle with flour; cook and stir 3 to 4 minutes or until flour is lightly browned. Gradually stir in broth until well blended. Bring to boil. Reduce heat to low; simmer 10 minutes or until slightly thickened, stirring occasionally. Add vegetable mixture, chicken, pearl onions, and peas; simmer 8 minutes or until chicken is cooked through, stirring occasionally. Meanwhile, cut bread into rounds with 3-inch cookie cutter. Place on baking sheet. Brush bread with oil and sprinkle with reserved seasoning mixture. Bake in preheated 350-degree oven 10 minutes or until toasted. To serve soup, ladle into soup bowls and top each with 1 crouton. Makes 8 (1-cup) servings.