Put all the mango slices in a mixing bowl. Add the li hing mui and li hing mui powder. Toss so that everything is evenly coated.
In a saucepan, combine the rice vinegar, apple cider vinegar, sugar, sea salt. Bring it all to a boil, stirring until the sugar and salt is dissolved. Remove from heat and cool for 5 minutes.
Pour the liquid over the bowl of mangoes. Let cool. Transfer to jars and store in the refrigerator for 24 hours before eating. Enjoy!
