Roasted Flat Mushrooms with Green Onion, Thyme & Butter

Bahan-bahan (4 porsi)

• 8 large mushrooms ((flat, portobello, "BBQ"), around 10 - 12cm / 4 - 4.5" wide, stem tips trimmed (Note 1))
• 100 g / 7 tbsp unsalted butter (, softened)
• 1 cup green onion ((US:scallions), thinly sliced)
• 1/3 cup parsley (, finely chopped)
• 1 tbsp fresh thyme leaves ((sub 1 tsp dried))
• 1/2 tsp salt
• 1/4 tsp black pepper
• 3 tbsp chopped scallions
• 1 dozen thyme stalks