Take a medium sized pot or dutch oven – it should be enough to fit the rice and the biryani masala and still have 2 – 3 inches space from the top.
Layer ½ the biryani masala at the bottom, and then add ½ the rice. Top with the remaining biryani masala, followed by the rice.
On top of the rice, add the coriander and reserved fried onions, along with green chilies.
Cover the pot and seal the lid with aluminium foil, or a kitchen cloth to seal the lid tightly. This is important as it helps in ensuring that the steam doesn’t escape. A heavy weight can be kept on the lid as well to help in this step.
Place the pot on an insulator – this can be a tawa, a flat gridle or a heat diffuser (available at Asian and Indian stores). If you have a cast iron Dutch oven or another heavy bottomed pan, this diffuser can be skipped. Turn the heat to medium for about 3 – 4 minutes. This will help in creating the steam. Once the steam is formed, turn heat to low / simmer, and cook for about 15 minutes on ‘dum’ – this means that the rice will cook in its own steam. Turn off the stove, and let the biryani rest for 10 minutes.
To serve, carefully mix the biryani using a small plate or a rice spoon. Move the rice from the sides, and lightly mix ensuring that the rice doesn’t break. Serve the leftover biryani hot with yoghurt or raita.