1 3-lb. piece seedless watermelon,
rind removed, cut into 1" chunks
2⁄3 cup sugar
1⁄2 cup cornstarch
1 tsp. vanilla extract
Whipped cream, to garnish
Roughly chopped pistachios, to garnish
Diced candied citron, to garnish, optional
Grated semisweet chocolate, to garnish
Ground cinnamon, to garnish
1. Purée the watermelon chunks in a blender or food processor until liquefied. Set aside.
2. Whisk together sugar and cornstarch in a 3-quart nonreactive saucepan. While whisking, drizzle in puréed watermelon. Bring the watermelon mixture to a boil over medium heat, while stirring constantly and scraping bottom with a wooden spoon. Boil, stirring constantly to prevent scorching, until it thickens slightly, about 5 minutes.
3. Remove the saucepan from the heat and whisk in the vanilla. Using a rubber spatula, push and scrape the watermelon mixture through a fine sieve into a 2-quart bowl. Cover bowl tightly with plastic wrap and refrigerate until set, about 4 hours. To serve, spoon the pudding between 6 small serving bowls and garnish with whipped cream, pistachios, citron (if using), and chocolate. Dust with the cinnamon.