In a dutch oven, melt butter over medium high heat. Add carrots, onion, celery, and garlic. Cook for 4-5 minutes, stirring frequently or until vegetables are tender. Add flour, tarragon, salt and pepper; cook, stirring constantly, for 2 minutes. Add broth and cream (evaporated milk or 2% milk); cook for 10-12 minutes, or until soup is thickened. Add chicken, rice, and peas; cook for 5-6minutes or until heated through. Garnish with toasted almonds, if desired.