In a large pot, combine the cooked rice, soy milk, vegetable broth, soy sauce, miso paste, sesame oil, garlic powder, ginger powder, and black pepper. Stir well to combine all the ingredients.
Heat the mixture over medium heat, stirring occasionally, until it starts to simmer.
Once simmering, reduce the heat to low and let it cook for about 10 minutes, stirring occasionally.
If using, add the diced tofu and frozen peas to the pot. Cook for an additional 5 minutes until heated through.
Remove from heat and stir in the chopped green onions.
Serve hot, garnished with additional green onions if desired.