Wash, pat dry and chop mushrooms into bite sized pieces and keep them aside.
Dry roast channa dal, dry red chillies and peppercorns in a skillet on a low-medium flame till dal turns golden brown (Approx 2 mins). Cool and grind them to smooth powder and keep aside.
Meanwhile, heat oil in a pan and add mustard seeds. When they start to pop and splutter, add curry leaves and sauté for few seconds.
Now mix in chopped mushrooms and sauté on medium heat. When they start to sweat add salt to taste, ground spice powder and mix well. Sauté gently on a medium flame for 1-2 minutes making sure that spice mixture doesn’t stick to bottom of the pan.
Add tamarind paste and sprinkle little water if necessary and mix well. Cook for another minute or so on medium flame sautéing in between.
Garnish with chopped coriander leaves and serve hot with Chapatti or plain steamed Rice or stuff it bewteen bread for spicy sandwich and enjoy.