Heat the butter and oil in a large pan.
Once the butter-oil mixture starts bubbling add chopped garlic and sauté for about a minute.
Add rinsed and wiped mushrooms and sauté for a minute.
Now add onions and sauté the onion until softened
Add thyme, green chilli, black pepper, and chilli flakes and cook the mushrooms for 4-5 minutes.
Season with salt and garnish with chopped green chilies and parsley.
Serve them hot.