Preheat your oven to 400°F.

Scrub the potatoes under running water and pat them dry.

Pierce each potato several times with a fork, then rub with olive oil and sprinkle with salt.

Place the potatoes directly on the oven rack and bake for 45-60 minutes, or until tender when pierced with a fork.

While the potatoes are baking, heat a skillet over medium heat. Add the diced mushrooms and sauté for about 5 minutes until they are browned and tender.

Add the chopped spinach and cook for an additional 2-3 minutes until wilted. Remove from heat and set aside.

Once the potatoes are done, remove them from the oven and let them cool for about 10 minutes.

Cut each potato in half lengthwise and scoop out the insides into a mixing bowl, leaving a thin layer of potato in the skin.

To the bowl with the potato insides, add the sautéed spinach and mushrooms, sour cream, half of the cheddar cheese, Parmesan cheese, garlic powder, onion powder, black pepper, and red pepper flakes if using. Mix until well combined.

Spoon the mixture back into the potato skins, mounding it slightly. Top each stuffed potato with the remaining cheddar cheese.

Place the stuffed potatoes back on a baking sheet and return to the oven for another 15-20 minutes, or until the cheese is melted and bubbly.

Remove from the oven and let cool for a few minutes. Garnish with chopped green onions if desired before serving.