01 - Whisk ube halaya, sweetened condensed milk, evaporated milk, heavy cream, and ube extract in a bowl until smooth and creamy. Set aside.
02 - In a saucepan, whisk together whole milk, heavy cream, and granulated sugar. Sprinkle gelatin or agar-agar over the surface and allow to bloom for 5 minutes. Warm the mixture over low heat, stirring constantly until the gelatin fully dissolves without boiling. Stir in vanilla extract and set aside to cool slightly.
03 - Arrange a layer of sponge cake at the base of each serving glass. Spoon a thick layer of ube mixture over the cake, followed by a layer of milk jelly. Repeat layers if there is space, finishing with milk jelly on top.
04 - Chill assembled glasses in the refrigerator for a minimum of 2 hours, or until the jelly is fully set.
05 - Top each chilled dessert with whipped cream and garnish with fresh ube cubes or purple sprinkles as desired before serving.