Toast the peppercorns and the fennel, coriander and cumin seeds in a small pan on medium heat. Once they are aromatic, take off the heat and allow to cool, then grind to a coarse powder and set aside.
Using a small blender, or mortar and pestle, make a coarse paste of the ginger and garlic, using as little water as possible. Set aside.
to cook
Heat the coconut oil in a kadai or wok. When hot, add the mustard seeds. These will start to pop after a few seconds - add the onion now, sprinkle with the salt and stir well.
Cook the onion, stirring frequently, on medium-low heat, for ten minutes or until it starts to turn a light golden colour.
Add the ginger and garlic paste and cook, stirring continuously until the raw aroma has gone. This will only take about two minutes.
Add the mushrooms, mix well, and cook on medium-low heat, stirring frequently. Take care with the stirring as you do not want to break up the mushrooms.
The mushrooms will take about 10 minutes to cook sufficiently, assuming they are halved, and not sliced. They will release a lot of moisture - continue to fry them until this moisture has nearly evaporated and the mushrooms are almost cooked.
Add the sliced red chilli and the curry leaves and mix well. Cook for another minute, stirring continuously.
Mix the ground turmeric and the ground peppercorns and spices. Sprinkle this over the mushrooms and stir gently until all the mushrooms are covered in this spice mix. Fry for another two minutes.
to serve
Sprinkle with coriander leaves. Stir them through and serve.
notes
As a variation, include thinly sliced green capsicum. Add this about halfway through cooking the mushrooms so that the capsicum retains some crunch