In a blender, layer the ingredients in the following order: cream of coconut, pineapple juice, pineapple chunks (if using), sugar, ice, rum.
Blend the mixture together until smooth, about 30 seconds to 1 minute.
Pour the piña colada mixture into cocktail glasses and top with sweetened whipped cream.
Garnish your piña coladas with a maraschino cherry and pineapple slice.
To store: if you're making this ahead of time, store the mixture in a freezer safe container in the freezer. Stir the mixture every 15 minutes to create a "slushie" consistency. To Make Virgin Piña Coladas: Omit the rum and replace it with 1/2-1 cup of cold water. Blend as instructed. For a lighter coconut flavor: Use 7 1/2 ounces of cream of coconut instead of the full can.