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Herb Stuffed Mushrooms
4.70 from 10 votes

Mashed Potato and Herb Stuffed Mushrooms with Caramelized Onions

Easy, Cheesy Mashed Potato and Herb Stuffed Mushrooms with Caramelized Onions and Parmesan Cheese. Vegetarian and gluten-free, this beautiful bite-size appetizer is the perfect game day or holiday appetizer.
Prep Time45 mins
Cook Time45 mins
Total Time1 hr 30 mins
Servings: 18 servings
Calories: 103kcal


  • 18 baby portabella mushrooms - stems removed - 18 to 24 mushrooms
  • 1 tablespoon olive oil
  • 1 tablespoon butter
  • 1 large yellow onion - sliced
  • 2 packages Idaho Spuds Country Butter Mashed Potatoes - prepared
  • ½ cup cooked wild or white rice - optional
  • 1 teaspoon finely chopped fresh thyme
  • 1 teaspoon finely chopped fresh rosemary
  • ½ teaspoon garlic powder
  • 1 teaspoon salt
  • ½ teaspoon pepper
  • 1 cup white cheddar cheese - shredded
  • ½ cup grated parmesan cheese - plus more for topping


  • Preheat oven to 350 degrees F. Line a large baking sheet with parchment paper. Prepare mushroom caps and place them on prepared baking sheet. Set aside.
  • Heat a large skillet over medium low heat. Add olive oil and butter and cook onions for 40-45 minutes, stirring occasionally, or until onions are completely caramelized.
  • While the onions are cooking, prepare the mashed potato filling. In a medium bowl mix together the prepared Idaho Spuds Country Butter Mashed Potatoes with the cooked wild rice, fresh thyme, rosemary, garlic powder, salt, pepper white cheddar cheese and parmesan cheese. Taste mixture, adding more salt and pepper as needed.
  • With a small spoon add the cheesy mashed potato mixture into the cavity of each mushroom, squeezing in as much as you can. Each mushroom will hold a different amount, some more some less.
  • When the onions are finished caramelizing (so worth the wait!), carefully scoop a little on to the top of each mushroom cap. Place stuffed mushrooms in the oven and bake for 20 minutes. Remove from the oven and top each mushroom cap with a little extra parmesan and fresh herbs and continue to cook for an additional 15-20 minutes.
  • Best served immediately.


Calories: 103kcal | Carbohydrates: 5g | Protein: 6g | Fat: 6g | Saturated Fat: 3g | Cholesterol: 17mg | Sodium: 266mg | Potassium: 335mg | Fiber: 1g | Sugar: 2g | Vitamin A: 180IU | Vitamin C: 0.7mg | Calcium: 130mg | Iron: 0.4mg
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