Preheat your oven to 350°F / 175°C.
In a medium saucepan, bring the water to a rolling boil.
Stir in the chopped sweet potato, uncooked rice, and 1/2 teaspoon (10 ml / 0.3 fl oz) of salt.
Bring it back to a boil, then reduce the heat to low, cover, and simmer for about 20 minutes, or until all the liquid has been absorbed and the rice is tender.
While the rice and sweet potatoes are cooking, prepare the creamy base.
In a large mixing bowl, combine the rinsed black beans, thawed edamame, half of the shredded Monterey Jack cheese (1/2 cup / 56 g / 1.98 oz), sour cream, undrained green chiles, chopped green onions, flour, fresh sage, minced garlic, and the remaining 1/2 teaspoon (10 ml / 0.3 fl oz) of salt.
Once the rice mixture is cooked, gently fold it into the bowl until everything is well combined.
Pour the mixture into an ungreased 2-quart / 1. 9-liter casserole dish and spread it into an even layer.
Sprinkle the remaining half of the Monterey Jack cheese over the top.
Bake uncovered for 30 minutes, or until the casserole is hot and bubbly and the cheese is melted and golden.
Let it rest for a few minutes before serving.
Garnish with toasted pumpkin seeds, if desired.