Place rice and water in a covered pan and cook per package instructions, or bring to a boil, then lower heat and simmer for 14 minutes, then remove from heat and let stand for 5 to 10 minutes.
Place oil in a wok and heat. Chop onion. Stir fry onion and garlic. Add galangal bark. Continue to stir fry until onion is translucent. Add chicken broth and coconut milk, juice of 3/4 lime, a splash of fish sauce, lemon grass, keffir leaves, and bring to an early simmer. Add chicken and mushrooms. Let simmer until chicken appears done, about ten minutes.
Slice the remaining quarter lime into four slices. In each of four serving bowls, add one scoop of cooked rice, a teaspoon of chopped cilantro, a squirt of sriracha hot sauce and a lime wedge. Spoon the soup over the rice and serve hot.