In a large bowl, add in the sifted flour, baking powder, salt and carom seeds. Combine and make a well in the center.
Add 4 tablespoons of oil and knead the dough until all the ingredients are well combined and the dough is crumbly and coarse.
Pour in the warm water gradually, kneading until the dough becomes nicely elastic and soft. After about 5 minutes of kneading the dough should be smooth.
Allow it to rest covered with cling film in the fridge for at least 30 minutes. (You can leave it overnight, if you have the time.)
Take the dough out of the fridge to return to room temperature before assembling the samosas.
For the samosa filling:
In a deep saucepan, heat about 2-3 tablespoons of oil and toast the cumin seeds until fragrant and sizzling. Then introduce the onion and sauté for about 5 minutes, until soft.
Stir in the chilies, ginger and spices and fry them for a few minutes before adding in the finely chopped potatoes.
Sauté everything together until the potatoes begin to soften at the edges (about 5-7 minutes), then add just enough water to cover the potatoes and cook for 15-25 minutes until the potatoes turn soft.
Next, it's time to add the peas and allow to cook with the other ingredients for a couple of minutes. Taste to mixture and season with salt and lemon juice according to your preference.
Take the samosa filling off the heat and mash it roughly, adding in the handful of cilantro, then let cool completely before continuing to form the samosas.
Assembling the Samosas:
Begin by dividing the room-temperature dough into 6 equal pieces. Keep them covered in plastic wrap to avoid them drying out while you work with each piece individually.
Take one piece of dough and roll it out onto a lightly floured surface with a rolling pin. Flatten it out to an oval until it's thin and translucent.
Cut the oval in half width ways and create a cone shape around the straight line. Dampen the straight edge with some water and pinch the edges of the cone together to seal them.
Take about a handful or a lemon-sized piece of filling and stuff it into the cone, then seal the samosa by flipping the round edge of the cone, forming a triangle.
Make sure all the edges are sealed (use water to make them more sticky if needed) and pinch them tightly. You can also press a fork along the sides to create a decorative pattern, if you like.
Deep fry the samosas in canola oil until the pastry becomes crispy and golden.