Add the soya chunks in a small saucepan and fill with water to cover them. Bring to a gentle boil over medium heat. Once soya is rehydrated and soft, remove from the heat and drain all water. Rinse in some cold water and drain, then set aside. Do not over cook the soya chunks or they will become too soft and fragile.
While soya chunks are cooking, in another saucepan, you can start preparing the basmati rice. Rinse the rice a couple of times with cold water until water is almost clear. Drain all water, then fill with 2 cups of water. Add in the cardamom pods and one cinnamon stick. Place on medium heat and bring to a boil. Once water starts to boil and rise, turn off the heat and cover the pan. Leave aside as the rice absorbs all the water. (There is not enough water in here to completely cook the rice, so the rice will only be half-cooked which what we want to achieve at this stage).
While rice is cooking, prepare the vegetables and the other ingredients.
Remove the seeds from the tamarind paste (if there are any) by diluting it in a little water and smooshing the pulp between your fingers. Then strain the tamarind liquid either using a strainer or just scoop out the seeds with your fingers and squeeze them in your hand to drain out all the liquid.
Add one tablespoon of turmeric powder in the peeled and cubed potatoes. Toss and mix well until potatoes are well coated. In a large deep thick bottom pot (we will cook the briyani in the same pot), heat 1 tablespoon of oil on medium-high temperature. Add in the potatoes and stir to evenly coat with the oil. Let cook while stirring a few times until potatoes are cooked up to 75%. Remove from the pan and set aside in a bowl or plate.
Next, still on medium-high heat, add one teaspoon of oil in the same pot. Place in the pre-boiled soya chunks. Add 1/2 teaspoon of cumin powder and a tablespoon of soy sauce or tamari. Fry the soya while stirring occasionally until some of their moisture have reduced and the chunks have picked a slightly crispy coating. Remove from the pan and set aside on the same plate as the potatoes.
To make the gravy, heat one tablespoon of oil on medium-high temperature. Add one tablespoon of mixed ginger and garlic paste. Let it sizzle for about 30 seconds then add in half of the onions. Let this sweat for about 2 minutes, then add 1 tablespoon of cumin powder followed by the garam masala and the coriander seed powder. Let the spices roast for about 5 seconds then add in the coconut milk and the diluted tamarind paste. Stir and let the gravy thicken. This may take about 10 minutes depending on how thick the coconut milk is. Once the gravy is almost paste-like, add half of the chopped coriander and half of the mint. Mix and add a little water if too thick. The mixture should not be too soupy but rather thick. Add the chillies and the remaining cinnamon stick.
Turn off the heat before adding in the vegetables.
Add the potatoes and soya chunks to the gravy and mix well. Next add in the carrots and okra and mix well with the rest. Now remove half of this vegetable-gravy mixture from the pan and set aside in another bowl or plate.
Spread the remaining vegetables evenly in the pot and sprinkle with a little salt.
Fluff the half-cooked rice to separate the grains. Layer half of the rice on the vegetables in the pot. Spread the rice evenly to cover the vegetables. Add a layer of the remaining herbs, the coriander and the mint. Then top with a layer of the remaining vegetables (from the bowl). You can add a little salt and spread evenly.
Before adding in the final layer of rice, add a teaspoon of turmeric powder to the rice and carefully mix it thoroughly so that the grains are coated. They don't need to be evenly coated, in fact, it is good to have grains of various tints of orange and yellow. Now add the rice in the pot and spread evenly to cover the vegetables. Top with the green peas and 3/4 cup of water poured evenly around. Cover and start cooking on medium heat. As soon as some steam starts to form, lower the heat to a lower temperature and cook for about 12 minutes. Then turn off the heat
While the briyani is cooking, you can fry the onions for a final touch to this dish. In a skillet, heat 1 tablespoon of oil and add in the onions. Fry while stirring occasionally until onions are brown and caramelised.
Add the fried onions on top of the rice (i.e. after you have turn off the heat for the pot). Then cover and let the briyani stand for another 10 minutes before serving.