Pomegranate-Coconut Trifle

In a saucepan, sprinkle gelatin over cold water; let stand until softened, about 5 minutes. Heat over medium until gelatin dissolves. In a 12- to 14-cup trifle dish or glass bowl, combine pomegranate juice, 1/3 cup sugar, and half of gelatin mixture (reserve remaining gelatin mixture at room temperature), stirring until sugar dissolves. Refrigerate until set, about 4 hours.

Meanwhile, in another saucepan, whisk together cornstarch, salt, cream of coconut, 1/2 cup heavy cream, and egg yolks until smooth. Add butter; cook over medium heat, stirring occasionally, until mixture comes to a boil. Cook, stirring, until it has the consistency of pudding. Strain through a fine-mesh sieve into a bowl; stir in vanilla. Cover surface with plastic wrap to prevent a skin from forming; let cool completely. Whip 1 cup heavy cream to stiff peaks; fold into pastry cream until smooth.

Arrange half of ladyfingers evenly in a single layer over pomegranate gelatin. Spoon pastry cream over top, spreading with an offset spatula until smooth. Top with remaining ladyfingers, in a single layer. Refrigerate; meanwhile, prepare an ice-water bath. In a bowl, stir together coconut water, 1/3 cup sugar, and reserved gelatin mixture until sugar dissolves. Place bowl over ice-water bath; let stand, stirring a few times, until mixture begins to thicken and mound, 20 to 30 minutes. Stir in pomegranate arils. Transfer mixture to trifle dish; smooth top. Refrigerate until set, at least 4 hours or, covered, up to 3 days.

Whisk remaining 1 cup heavy cream and 2 tablespoons sugar to soft peaks. Spoon over trifle; sprinkle with toasted coconut. Spoon into bowls and serve.