In a medium sized saucepan, place rice and broth together and bring to a boil over medium-high heat; cover, reduce heat and simmer until the water is absorbed, about 30-35 minutes.
Remove from heat and set covered pot aside until needed.
Slice the tops off the bell peppers, remove and discard the seeds and membranes from the inside of each pepper (keep the top with stem intact) and set aside.
Preheat oven to 350°F. Drizzle oil into a large sauté pan and place over medium-high heat. Add onion and chopped mushrooms and sauté for 1-2 minutes, until they begin to tenderize. Add minced garlic, cumin, paprika, pepper, and a generous pinch of salt. Cook for 4-5 minutes, until all the vegetables are cooked thoroughly.
Stir in spinach and cook until heated through and the spinach is wilted. Add in cooked rice and check seasoning - adjust adding additional salt, pepper, or cumin to taste.
Remove from heat and stir in chopped parsley.
Fill each pepper with the rice mixture and place into a baking dish (make sure the baking dish is the right size - you want the peppers to be semi-snug so they don’t tip over while baking).
Add a little water to the bottom of the baking dish to steam the peppers while baking. Cover dish with aluminum foil and place onto the middle rack of the pre-heated oven. Bake for 30-40 minutes, or until peppers are soft and filling is hot.