Ingredients

• 1 tbsp butter
• 1 large onion, thinly sliced
• 1/4 cup beef broth
• 1/2 tsp garlic, minced
• 1 tsp fresh thyme leaves
• 1 tsp Worcestershire sauce
• 1 tbsp oil
• 12 whole button mushrooms, stems removed
• 1/4 cup shredded Gruyère cheese
• Salt and pepper to taste
• Chopped fresh parsley for garnish

Preparation

Preheat the oven to 350°F.
In a skillet, melt butter over medium heat. Add onions and cook, stirring occasionally until they begin to caramelize, between 20 and 25 minutes. Add broth, garlic, thyme leaves and Worcestershire sauce. Cook for another 2 to 3 minutes, or until liquid has mostly evaporated. Remove from pan and set aside.
In the same pan, add the oil and whole mushrooms. Cook for 3 to 4 minutes over medium-high heat. Remove from heat and transfer mushrooms into an oven-safe baking dish, stem side facing up.
Stuff mushrooms with onion mixture and top with Gruyère cheese.
Bake for 10 to 12 minutes or until mushrooms are cooked through and cheese is melted and bubbly. Garnish with chopped parsley.
Serve immediately or store in ther refrigerator for up to 3 days.