Caramelized Onion Stuffed Mushrooms are the ultimate combination of sweet onions paired with cheese. No sugar added. A favorite for any mushroom lover. Yum!Prep time includes time for caramelizing onions. You can cut this time by 30 minutes if you use premade caramelized onion jam which can be purchased at specialty stores.The onions can be made days ahead. You can also stuff the mushrooms ahead of time and then pop them in the oven when you are ready.
24whole white button or cremini mushroomswashed and stems removed
1tablespoonolive oilfor drizzling
½cupfreshly grated Swiss, Gruyere, or Jarlsberg cheeseabout 2 ounces or so
Instructions
For Caramelized Onions:
Peel the onions and slice them in half from root to stem. Notch out the root and slice the onions into ¼” slices. When slicing, slice in the direction from root to stem.
In a large skillet over medium heat, melt the butter then add onions. Sprinkle with salt and pepper and cook for 15 minutes, stirring occasionally. You may need to lower heat if onions are browning too quickly. After onions are lightly browned and a fond develops on the bottom of the pan, reduce heat to low and continue cooking for another 10 minutes. The fond is the brown coating on the bottom of the pan from the sugar drawn out from the onions.
Add balsamic vinegar to deglaze pan, scraping up the fond as it loosens.
Cook the mixture for another 3 - 5 minutes, scraping and deglazing skillet. Remove from the heat and set aside to cool.
For Mushrooms:
Preheat oven to 400 degrees.
Place the mushrooms bottom side up in a baking dish and drizzle with the olive oil.
Stuff the cavity of each mushroom with the caramelized onions, then sprinkle tops with cheese.
Bake for 15 to 20 minutes. Serve warm.
Notes
You can use premade onion jam found in specialty stores.