Once the syrup has reached 240° Fahrenheit, remove pan from heat and allow the temperature of the syrup to reduce to 210° Fahrenheit. This can take anywhere from 7-10 minutes. You can help it along by partially submerging the pan in a bowl of ice water and stirring the syrup.
Once the syrup has reached 210° Fahrenheit, carefully pour the syrup (be careful – It’s STILL HOT!) into the mixing bowl with the bloomed gelatin. Start your mixer, on low at first as you add the syrup, and then increase the speed to high. Allow the mixture to double in volume. While the mixer doubles in volume, quickly combine the coconut milk and coco Lopez.
When the mixture has doubled, add the coconut milk and Coco Lopez mixture 1 tablespoon at a time, allowing the mixture to thicken and become fluffy with each addition. Add the rum and whip on high until the becomes fluffy once one more.
Turn off the mixer and using a silicone spatula very lightly sprayed with PAM, pour the mixture into the prepared pan. Smack the pan a few times against your counter to remove air bubbles and sift some of your prepared coating over the top of the marshmallow mixture.
Cover with plastic wrap and refrigerate for at least 4 hours.