In a mortar and pestle, crush coriander seeds, fennel seeds, and cumin seeds into a coarse powder. Set it aside.
In a pan, heat oil and sauté the coarsely crushed masala. Add green chili paste and ginger paste, sauté again.
Now, add boiled and roughly mashed potatoes, green peas, chaat masala, salt, black pepper powder, kasuri methi, garam masala, and coriander leaves. Mix well.
Mash the stuffing slightly with a masher.
The samosa stuffing is now ready.