1. Sprinkle gelatin over 1/4 cup milk in a small bowl; stir until moistened. Let stand 5 minutes. (Mixture will be lumpy.)
2. Meanwhile, carefully remove 3 (2- x 1-inch) strips of rind from 1 navel orange using a vegetable peeler. Reserve orange for another use.
3. Cook heavy cream, granulated sugar, and orange rind strips in a saucepan over medium-low heat, stirring occasionally, 4 minutes or until sugar is dissolved. Remove from heat, and add gelatin mixture, stirring until mixture is dissolved. Stir in vanilla and remaining 3/4 cup milk. Discard orange rind strips.
4. Pour mixture into 6 (4-oz.) dessert glasses or wineglasses. Cover and chill 8 hours.
5. Peel and section remaining 2 navel oranges. Roll orange sections in turbinado sugar. Top panna cotta with Buttery Orange Curd and sugared oranges. Garnish, if desired. Store leftover panna cotta in refrigerator up to 3 days.
Note: We tested with HAIN Pure Foods Natural Turbinado Sugar.