Heat the oil in a pan over a medium heat until warm but not smoking.
Add the chopped onion and cook gently for a few minutes until soft and lightly translucent.
Stir in the cumin seeds and garlic paste, cooking briefly until fragrant without letting the garlic colour.
Sprinkle in the chilli flakes, crushed coriander seeds, chilli powder, turmeric, and salt, then cook for a couple of minutes so the spices release their aroma.
Add the frozen peas and cook until they soften and are evenly coated in the spiced mixture.
Crumble in the boiled potatoes and cook for a few minutes, lightly mashing them while keeping some texture.
Mix through the fresh coriander, then remove from the heat and allow the filling to cool completely.
In a bowl, combine the plain flour, carom seeds, salt, and oil, rubbing everything together until it resembles coarse crumbs.
Gradually bring the mixture together into a firm dough, kneading until smooth and elastic.
Cover the dough and let it rest for at least 30 minutes to relax the gluten.
Divide the rested dough into small balls, then roll each one out into a circle that is neither too thin nor too thick.
Cut each circle in half, shape one half into a cone, and seal the edge with a little moisture to hold its form.
Spoon the cooled potato filling into the cone without overfilling, then seal the open edge securely; at this stage, the samosas can be frozen if desired.
Heat oil in a deep pan to a medium temperature, ensuring it is hot enough to cook evenly without browning too quickly.
Fry the samosas gently, turning halfway, until they are crisp and evenly golden all over.
Remove from the oil and allow excess oil to drain briefly before serving hot with chutney.
