In a bowl, combine 2 cups of white sugar, 1 cup of water, 1 cup of white wine vinegar, and 2 tablespoons of honey.
Add the peeled, pitted, and cut mango to the bowl, stirring to coat.
Cover the bowl with plastic wrap and refrigerate for 8 hours or overnight.
Drain the liquid from the mango, reserving 1/4 cup of the liquid for later use.
In a pot, heat 1 tablespoon of olive oil over medium heat.
Cook and stir 1 minced shallot and 1/2 teaspoon of minced ginger root until slightly tender, about 5 minutes.
Add 1 cup of Arborio rice to the pot, cooking and stirring until slightly toasted, 1 to 2 minutes.
Pour 1 1/2 cups of chicken broth and 1/2 cup of coconut milk over the rice, bringing it to a boil.
Cover the pot, reduce heat to medium-low, and simmer until rice is tender and liquid is absorbed, about 20 minutes.
In a skillet, combine the mango, 1/4 cup reserved vinegar mixture, and 1/4 cup of white wine over medium heat.
Cook and stir until warmed, about 2 minutes.
Add 1 1/2 cups of shredded spinach and cook until wilted, about 1 minute.
Stir the rice mixture and 3/4 cup of grated Parmesan cheese into the mango mixture.
Remove from heat and let sit until liquid absorbs and cheese melts, about 7 minutes.
Place 1 cut watermelon slice on a serving platter and top with risotto.
Garnish with the 2nd cut watermelon slice atop the risotto.