Peel the mangos and take out the seed. Slice into thick long pieces. Don't slice it too thin or the mangos will become limp and will not be crunchy. These mangos were cut about a ½-inch thick. Transfer to a large bowl. If you have li hing mui, you can add these to the bowl, too.
Heat up white sugar, brown sugar, vinegar and Hawaiian sea salt on medium heat to form the syrup. Constantly stir the mixture and use clean and dry utensils. Make sure the pot and utensils aren't wet.
Pour the syrup into the bowl of mangos. With gloved hands, mix everything together so that the syrup is covering all the surface area of the mangos. The gloves will stop any contamination from your skin.
Transfer mangos and syrup into containers. If mangos are floating above the syrup, place a small bowl under the lid before you close it so the pickling sauce is touching every mango slice.