01 - Coat a 9x9-inch baking pan thoroughly with butter or nonstick cooking spray to prevent sticking.
02 - Place butter in a large saucepan over low heat. Once melted, add mini marshmallows and stir continuously until completely melted and smooth.
03 - Add ube halaya and ube extract to the melted marshmallow mixture. Stir vigorously until fully incorporated and the mixture achieves a vibrant purple color.
04 - Remove saucepan from heat. Immediately pour in crispy rice cereal and fold gently with a spatula until all pieces are evenly coated with the purple mixture.
05 - Transfer the mixture to the prepared baking pan. Using a greased spatula or wax paper, press firmly and evenly to distribute the mixture uniformly.
06 - Drizzle melted white chocolate over the surface and sprinkle with toasted coconut flakes if desired.
07 - Allow treats to cool at room temperature for at least 1 hour. Cut into 16 equal squares and serve.