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Sautéed Spinach, Mushrooms, and Caramelized Onions

Sautéed Spinach, Mushrooms, and Caramelized Onions is a versatile, flavor-packed side dish that pairs beautifully with chicken, steak, pasta, or grains. Built on the natural sweetness of slow-caramelized onions, the earthiness of mushrooms, and the freshness of spinach, this recipe brings restaurant-quality flavor to your home kitchen. Add the optional creamy Parmesan sauce for a richer, more indulgent version. Whether served as a healthy side, a topping for proteins, or even as a vegetarian main, this dish offers warmth, comfort, and incredible depth.
Prep Time10 minutes
Cook Time40 minutes
Total Time50 minutes
Servings: 16

Ingredients

Caramelized Onions

  • 1 tablespoon olive oil
  • 3 medium or large onions sliced
  • Pinch of salt
  • 1 tablespoon balsamic vinegar

Cooked Mushrooms & Spinach

  • 1 tablespoon olive oil
  • 8 oz mushrooms button, shiitake, etc., sliced
  • 3 garlic cloves minced
  • Pinch of salt
  • 6 oz fresh spinach

Optional Cream Sauce

  • ⅓ cup heavy cream
  • ¼ cup milk
  • ½ cup shredded Parmesan cheese
  • ¼ teaspoon salt

Instructions

Caramelize the Onions

  • Heat olive oil in a large skillet over medium-high heat.
  • Add sliced onions and cook for 10 minutes, stirring constantly.
  • Reduce heat to medium and cook for 10 more minutes, stirring frequently.
  • Add a pinch of salt.
  • Continue cooking for another 10 minutes on medium or low heat.
  • Remove from heat and add balsamic vinegar.
  • Stir to deglaze the pan and coat the onions.
  • Transfer onions to a plate.

Cook Mushrooms & Spinach

  • Heat olive oil in the same skillet over medium heat.
  • Add mushrooms and sprinkle with salt.
  • Cook for 5 minutes, stirring occasionally.
  • Add spinach and stir on low heat until wilted.

Make the Cream Sauce (Optional)

  • Add heavy cream and milk to the skillet.
  • Bring to a brief boil, then reduce to a simmer.
  • Add Parmesan and salt.
  • Stir until cheese melts and sauce thickens.
  • Add caramelized onions back to the skillet.
  • Adjust thickness with more cream (to thin) or Parmesan (to thicken).

Notes

Ingredient Substitutions

  • Use kale or Swiss chard instead of spinach.
  • Replace Parmesan with Pecorino Romano for sharper flavor.
  • Add thyme or rosemary for herbal depth.

Make-Ahead & Storage

  • Keeps for 3–4 days in the fridge.
  • Reheat gently on the stovetop.
  • Freezing is not recommended for the creamy version.

Serving Variations

  • Serve over grilled chicken, steak, or tofu.
  • Toss with pasta for a full meal.
  • Add to omelets, sandwiches, or wraps.

Avoid Common Mistakes

  • Don’t rush the onions—proper caramelization takes at least 30 minutes.
  • Avoid overcrowding the mushrooms or they’ll steam instead of brown.
  • Add spinach last to prevent overcooking.