01 -  In a mixing bowl, combine ube halaya, sweetened condensed milk, evaporated milk, heavy cream, and ube extract. Whisk together until the mixture is smooth and uniform. Set aside. 
 02 -  Pour whole milk, heavy cream, and granulated sugar into a small saucepan. Sprinkle gelatin or agar-agar powder over the mixture and let it stand for 5 minutes. Warm the mixture gently over low heat, stirring frequently until the gelatin or agar fully dissolves without boiling. Add vanilla extract, stir to incorporate, and remove from heat. Allow to cool slightly. 
 03 -  Arrange a layer of sponge cake at the bottom of each serving glass. Spoon a generous portion of ube mixture over the cake layer. Pour milk jelly over the ube layer. If glass height allows, repeat the layering as desired, finishing with milk jelly. 
 04 -  Transfer the assembled glasses to the refrigerator. Chill for at least 2 hours, or until the jelly is fully set. 
 05 -  Before serving, top each trifle with whipped cream and garnish with fresh ube cubes or purple sprinkles, if desired.