Rinse the brown rice under cold water until the water runs clear to remove excess starch.
In a small saucepan, combine the rice and bone broth; bring to a boil, then reduce heat to low and simmer covered for 40-45 minutes until all liquid is absorbed.
While the rice is cooking, season the chicken breast evenly with sea salt, black pepper, and garlic powder.
Heat the olive oil in a medium skillet over medium-high heat and sear the chicken for 5-7 minutes per side until golden brown and cooked through.
Remove the chicken from the skillet and let it rest for 5 minutes before slicing into bite-sized pieces.
In the same skillet, add the sliced mushrooms and sauté for 3-4 minutes until they are browned and tender.
Add the fresh spinach to the mushrooms and stir for 1 minute until just wilted.
Fluff the cooked bone broth rice with a fork and fold in the sliced chicken, mushrooms, and spinach before serving warm.