Remove part of cauliflower stem, leaving whole head intact. Bring 1 inch of water to a boil in large saucepan or Dutch oven. Place cauliflower, stem end down, in saucepan; cover and steam 15-20 min or until crisp-tender.
Meanwhile, in another large saucepan, bring 2 quarts water to a boil; add peppers. Cover; simmer 10 min or until skin loosens, turning peppers once or twice during cooking. Drain; rinse with cold water. Remove and discard skin, stem and seeds. Coarsely chop peppers. In food processor bowl with metal blade, process peppers, tarragon and salt until smooth. With processor running, slowly add half & half; process until blended.
To serve, place hot cauliflower, stem end down, on large plate; sprinkle with chopped parsley. Serve with sauce.
Nutrition Info Per Serving: Calories 51.3 Total Fat 2.5 g Saturated Fat 1.5 g Polyunsaturated Fat 0.2 g Monounsaturated Fat 0.7 g Cholesterol 8.1 mg Sodium 232.1 mg Potassium 333.4 mg Total Carbohydrate 6.0 g Dietary Fiber 2.5 g Sugars 2.7 g Protein 2.5 g