Make the mushroom pesto. Pour olive oil into a frying pan and add chopped onion and garlic. Fry until golden brown, add green onion. Continue frying for another 1 minute. Put mushrooms, sun-dried tomatoes and chilli peppers into the pan. Simmer the pesto for 5 minutes. Add walnuts and parsley, pour in 50 ml of water, add salt. Cook for another 3 minutes. Turn off the heat and cool. Transfer the sauce to a blender bowl and mix until puree consistency.