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, approximately 5 minutes.
03 - Add ube halaya and ube extract (if using) 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 with the purple marshmallow mixture.
05 - Transfer the mixture to the prepared baking pan. Using a greased spatula or wax paper, press the mixture firmly and evenly into the pan to create a uniform surface.
06 - If desired, drizzle melted white chocolate across the top surface and sprinkle with toasted coconut flakes for added texture and visual appeal.
07 - Allow the treats to cool at room temperature for a minimum of 1 hour until completely set. Cut into 16 equal squares using a sharp knife.