Clean and chop 250 grams of mushrooms into bite-sized pieces. Set aside.
In a pan, dry roast 1 tablespoon coriander seeds, 1 teaspoon cumin seeds, 1 teaspoon fennel seeds, 1 teaspoon black peppercorns, 4-5 dry red chilies, and 2 tablespoons grated coconut until fragrant. Cool and grind into a fine powder.
Heat 2 tablespoons of oil in a pan. Add 1 teaspoon mustard seeds and let them splutter.
Add 1 finely chopped onion and sauté until golden brown.
Add 1 teaspoon ginger-garlic paste and sauté for 2 minutes.
Add the chopped mushrooms and cook for 5 minutes, stirring occasionally.
Add the ground spice powder, 1/4 teaspoon turmeric powder, and salt to taste. Mix well and cook for 2-3 minutes.
Add 1 cup of water and bring the curry to a boil. Reduce the heat and simmer for 10-12 minutes, or until the mushrooms are cooked and the gravy thickens.
Garnish with chopped coriander leaves and serve hot with rice or roti.