Soak black rice in a medium bowl of filtered water for 15-30 minutes. Drain using metal sieve, and rinse several times in fresh running water.
Add rice, 1 1/4 cup full fat coconut milk, 1/2 cup filtered water, and 1 teaspoon sea salt to a small saucepan. Bring to a boil over medium-high heat, then cover and reduce heat to maintain a simmer. Let cook about 30 minutes, or according to your package instructions. Remove from heat, and let sit one minute before removing the lid and fluffing with a fork. It rice seems dry, add a couple of extra tablespoons of coconut milk.
While the rice is cooking, chop mango, cilantro and scallions, then set aside.
Add cooked rice, mango, cilantro, onion, salt and pepper to a medium bowl. Toss to combine, adjust seasonings to taste, and serve immediately.
Rice will keep a couple of days in the refrigerator.