Preheat oven to 400°F (200°C). Pierce sweet potatoes with a fork a few times. Place on a baking sheet and roast for 40–50 minutes, or until tender. Let cool slightly before handling.
Meanwhile, heat olive oil in a skillet over medium heat. Sauté onions for 2–3 minutes until translucent. Add garlic and cook for 30 seconds. Stir in mushrooms and cook until they release their moisture and brown, about 5–7 minutes. Add spinach and rosemary; cook until spinach wilts. Season with salt and pepper. Remove from heat and stir in half of the feta.
Slice each sweet potato open lengthwise without cutting all the way through. Fluff the insides with a fork. Spoon the spinach-mushroom mixture into the potatoes. Sprinkle the remaining feta over the top.
Garnish with a sprinkle of fresh rosemary or parsley if desired. Serve warm and enjoy!
Notes
Add Protein: Toss in cooked quinoa, chickpeas, or shredded chicken for a protein boost.
Vegan Option: Use a dairy-free feta substitute or skip the feta.
Make Ahead: Bake the sweet potatoes and prepare the filling in advance; assemble just before serving.