01 - Grease a 9x9-inch baking pan with butter or nonstick cooking spray to prevent sticking.
02 - In a large saucepan, melt the butter over low heat. Add the mini marshmallows and stir continuously until completely melted and smooth, being careful not to scorch the mixture.
03 - Stir in the ube halaya and ube extract if using, mixing until fully incorporated and the mixture achieves a vibrant purple color throughout.
04 - Remove the saucepan from heat and immediately fold in the crispy rice cereal. Stir gently with a spatula until all the cereal is evenly coated with the purple marshmallow mixture.
05 - Transfer the mixture to the prepared pan. Using a greased spatula or wax paper, press the mixture evenly and firmly into the pan to create a uniform layer.
06 - If desired, drizzle melted white chocolate over the top and sprinkle with toasted coconut flakes while still slightly warm for better adhesion.
07 - Let cool at room temperature for at least 1 hour until completely set. Cut into 16 equal squares using a sharp knife.