Start by boiling the potatoes in a large pot of water until they are tender. Once cooked, drain them and let them cool completely. After cooling, peel the potatoes and mash them roughly with a potato masher or fork. Set this aside.

In a large non-stick pan, heat the oil and add the cumin seeds, allowing them to sizzle for a moment. Then, add the ginger, chillies, and onions. Sauté these ingredients for about 3-4 minutes until the onions become translucent but not browned.

Next, incorporate the mashed potatoes, peas, turmeric, amchur, ground coriander, ground fennel, and salt into the pan. Stir everything together thoroughly and cook for an additional 2-3 minutes while stirring continuously. Remove the mixture from the heat and spread it onto a plate. Mix in the chopped coriander and let it cool completely.

In a large bowl, combine the flour with ajwain and salt. Create a well in the center and pour in the oil. Using your fingertips, rub the flour and oil together until the mixture resembles fine breadcrumbs, similar to making shortcrust pastry.

Gradually add the warm water and mix with your hands to form a rough, shaggy dough. Knead this dough for about 10 minutes until it becomes smooth. Cover it with a damp tea towel and let it rest for 30 minutes.

After resting, divide the dough into 9 equal portions, shaping each into a round ball. Keep them covered with a damp tea towel to prevent drying out. Each ball will yield 2 samosas, resulting in a total of 18.

Take one dough ball and lightly coat it in flour. On a clean surface, roll it out into an oblong shape, approximately 12 cm wide and 18 cm long. Cut this oblong in half to create two semicircles.

Position one semicircle flat on the surface with the straight edge facing you. Roll it out slightly to make it thinner and taller. Fold the upper left corner towards the center, then add a bit of water along the centerline. Bring the upper right corner to meet the waterline and gently press the edges together to seal.

Open the pocket you just formed and fill it with about 2 tablespoons of the cooled potato and pea mixture. To create a base for the samosa, place your finger in the center of the rounded edge and make a small fold, pinching to seal it.

Dab some cold water on the inner seams of the open edge and press to seal, ensuring no air is trapped inside. Repeat this process for the remaining dough balls, keeping them covered to avoid drying out.

Once all the samosas are shaped, let them air dry for 45 minutes until the surface feels rough and sandy. This step helps prevent air bubbles during frying.

In a large pan or wok, heat the oil until it is warm but not hot—around 120°C/250°F. Be cautious not to overheat, as this can lead to uneven cooking.

Fry the samosas in batches, ensuring not to overcrowd the pan. Gradually increase the temperature, keeping it below 150°C/300°F. Cook the samosas for about 25 minutes until they are golden and crispy, adjusting the heat if they brown too quickly.

After frying, drain the samosas on a plate lined with absorbent kitchen paper.