Preheat oven to 325°.
Heat 1/2 cup sugar in a small heavy saucepan; cook over medium-high heat, stirring constantly with a wooden spoon until sugar melts and turns light brown. Quickly pour hot caramel into 6 (6-ounce) custard cups or ramekins coated with cooking spray. Carefully tilt each cup to coat bottom evenly. Place cups in a 13 x 9-inch baking pan; set aside.
Combine remaining sugar, eggs, egg whites, and next 4 ingredients in a large bowl. Pour mixture evenly over caramel into prepared cups. Add hot water to pan to a depth of 1 inch. Bake at 325° for 50 minutes or until a knife inserted near center comes out clean.
Remove cups from pan; cool completely on a wire rack. Cover and chill at least 8 hours. Loosen edges of custard with a sharp knife, and invert onto serving plates, letting melted caramel drizzle over top. Garnish with toasted coconut, if desired.