Melt butter over medium heat; sauté shallots for 3 to 5 minutes or until softened. Stir in flour; cook for 2 minutes. Add milk, a splash at a time, until smooth. Stir in cream; bring to simmer. Cook, stirring constantly, for 5 to 7 minutes or until thickened. Whisk in Dijon, salt and pepper. Remove from heat. Preheat oven to 375°F. Place two cannelloni in each of 4 baking dishes. Top with sauce and Gruyère. Bake for 25 to 30 minutes or until tender and heated through. Broil for 2 to 3 minutes or until cheese is golden brown. Combine parsley, chives and tarragon; sprinkle over top before serving.