In a large nonstick pan, melt butter, then add uncooked brown rice and saute the rice for 3 minutes. Add broth, and simmer for 35 to 40 minutes, stirring frequently until rice is cooked al dente. Add additional broth or water if it evaporates before the rice is done.
Heat the oven to 375°F. While the oven is heating, stir the soup in the pan and simmer an additional 10 minutes until the soup has reduced into a thick sauce stirring frequently. Add half of the cheese and half of the basil, stir to incorporate.
Place the mushrooms on a parchment-lined baking sheet and bake for 10 minutes, then blot the mushrooms with a clean towel to remove excess moisture.
Stuff each mushroom with a large spoonful of rice, add a dollop of the remaining cheese, salt and pepper to taste, and then return to the oven for an additional 10 minutes. Serve topped with remaining basil.
This nutritional information refers to each serving of the entire recipe and not just the products used as ingredients.