Preheat oven to 450°.
Combine the first 4 ingredients in a 3-quart casserole. Bake at 450° for 40 minutes, stirring once. Remove from oven. Stir in mint; set aside. Reduce oven temperature to 325°.
Combine the milk, orange rind, and vanilla bean in a medium saucepan. Bring to a simmer over low heat; cook 10 minutes. Remove from heat; discard vanilla bean. (If using vanilla extract, remove milk mixture from heat; stir in extract.)
Combine 3/4 cup sugar and water in a small heavy saucepan over medium heat; cook until golden (about 15 minutes). Immediately pour into a 9-inch round cake pan, tipping quickly until the caramelized sugar coats bottom of pan.
Combine milk mixture, 3/4 cup sugar, eggs, and egg whites in a large bowl; stir well with a whisk. Pour mixture into prepared pan. Place cake pan in a large shallow pan; add hot water to shallow pan to a depth of 1 inch. Cover with foil; bake at 325° for 50 minutes or until a knife inserted in center comes out clean. Remove cake pan from water; cool completely on a wire rack. Cover and chill at least 3 hours.
Loosen the edges of the flan with a knife or rubber spatula. Place a plate, upside down, on top of pan; invert flan onto plate. Drizzle any remaining caramelized syrup over flan. Cut flan into 8 wedges; top with pineapple mixture.