01 - Generously grease a 9x9-inch baking pan with butter or nonstick cooking spray, ensuring complete coverage to prevent sticking.
02 - Place unsalted butter in a large saucepan over low heat. Once melted, add mini marshmallows and stir continuously until completely melted and smooth, approximately 3-5 minutes.
03 - Add ube halaya and ube extract to the melted marshmallow mixture. Stir vigorously until fully incorporated and the mixture achieves a uniform vibrant purple color.
04 - Remove saucepan from heat immediately. Pour crispy rice cereal into the ube mixture and fold gently with a spatula until all cereal pieces are evenly coated.
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, while the treats are still slightly warm.
07 - Allow the treats to cool completely at room temperature for at least 1 hour. Cut into 16 equal squares using a sharp knife.