In a heatproof bowl that will fit a large pot with tight fitting lid, mix 6 Tbsp glutinous rice flour with the sugar and water until well combined. 

Bring 2" of water to a boil in large pot over high heat. Place a steamer rack into the pot and then the bowl with the rice flour mixture on top of the rack. Cover and steam for 5 minutes. Remove from heat and let cool for 5 minutes. 

In the meantime, toast the remaining glutinous rice flour in a dry frying pan over low heat for 5 minutes, stirring constantly for even cooking. Remove from heat.

Lightly dust a clean work surface and your hands with some of the toasted glutinous rice flour, knead the dough until it is smooth and pliable. If it starts to get sticky, you may need to use more flour to dust. Divide the dough into two even pieces and use a rolling pin to flatten it into a thin, even oval that's large enough to wrap one of the mango halves. 

Place the mango onto the dough, curved-side down and gently pinch the open edges together to completely wrap around and enclose the mango without any gaps. If there are holes, then just stretch the dough slightly and pinch it closed. Wrap up the second piece of mango. Dust off any loose, excess glutinous rice flour and enjoy!