1/4 Ripe watermelon 2/3 c Sugar 1/2 c Cornstarch 1 ts Vanilla extract 2 tb Chopped, blanched pistachios 1/2 oz Semisweet chocolate - coarsely grated 3 tb Candied citron - rinsed and chopped Cinnamon; for finishing Popular in Palermo, this dessert carries the humble watermelon to new heights of sophistication. SPOON THE FLESH AWAY from the rind of the melon into a large bowl. Remove seeds and liquefy in food processor or blender. Combine sugar and cornstarch in a 3-quart non-reactive saucepan and add watermelon juice gradually, whisking it in. Place over low heat and bring to a boil, stirring constantly with a flat-edged wooden spatula. At the boil, continue cooking about 5 minutes, stirring constantly, over lowest heat. Remove from heat, stir in vanilla extract and pour into a mixing bowl. Cool to room temperature, stirring occasionally to prevent a skin from forming on the surface. After the gelo has cooled, stir in the remaining ingredients, except the cinnamon. Pour into a glass serving bowl and chill. To serve the gelo, spoon into dessert bowls and sprinkle with cinnamon at the table.