Clean and quarter button mushrooms.
Heat vegetable oil in a pan, crackle fennel seeds and fresh curry leaves.
Add finely sliced onions, ginger paste, and garlic paste; sauté until golden brown.
Add mushrooms and salt; cook on high heat until mushrooms release their moisture and it evaporates completely.
Stir in freshly cracked black pepper powder, toss continuously for 3 minutes until dark and roasted, then serve hot.