Heat the butter in a non-stick pan and sauté the onions till they are translucent.
Add the green chilli and sauté for a few seconds. Add the mushrooms, oregano and salt.
Cook for a few minutes on very high heat until the mushrooms soften.
Divide into eight equal portions and keep aside.
Apply butter on bread slices. Heat a non-stick tawa and toast the bread slices till they are golden on both the sides.
Top each toast with a portion of the mushroom mixture and grated cheese.
Place the toasts on a plate and toast in microwave HIGH (100%) for one minute.
Remove from microwave and cool.
Cut each toast into triangles, garnish with the parsley and serve immediately.