In a blender, add 1 medium onion, 6 garlic cloves, 1 inch ginger, 2 green chilli, 1/2 tsp pepper corns, 1 tsp fennel seeds, 1 tsp cumin seeds, 1 tsp coriander seeds and coarsely grind them.
In a pan, add 1 tsp oil, add the blended paste and cook for 5 mins in medium flame until the raw smell goes away.
Next blend 2 tomatoes and add in the pan.
Add 1 tsp garam masala, 1/2 tsp turmeric powder, 1/4 tsp chilli powder, salt and let it cook for 10 mins in medium flame.
Next, add chopped mushrooms and cook for 2-3 mins.
Add 1/3 cup thin coconut milk and cook for 5 mins in medium flame.
Add 1 tsp chopped coriander. It is done.