Put the Basmati Rice in a bowl and rinse it very well under running water, taking care to be gentle when stirring the rice so you don't break the rice grains. Rinse until most of the starch has been washed, and the water is almost clear and no longer cloudy.
Cover the rinsed rice with water (approx. 2 inches/4 cm above rice level), and let it soak for 30 minutes before cooking.
After 30 minutes, strain the soaked rice (in a collinder or seive) from all the the water.
Gently heat 1 tablesoon of Oil in a heavy-based (preferrably non-stick), wide cooking pot. Make sure the oil covers the whole base of the pot.
Add the strained rice to pot, then the 3 cups of Water, remaining Oil, Salt, and stir gently for a few seconds, taking care not to break the rice grains (just enough for the salt to mix in the water).
Bring to a gentle boil. As soon as the water begins to boil, turn the heat down to a medium/low, allowing contents to simmer gently. Cover the pot with a tight lid (alternatively, use a clean dry teatowel wrapped around the lid to ensure no air/steam escapes the pot. You can also use baking foil instead of the teatowel to keep the pot contents air-tight).
Once the rice has been simmering gently for 10 minutes, and you can almost hear the rice at the bottom of the pot making crisp sounds, turn the heat down to a low heat, and let it steam gently for a further 20 minutes - this will ensure the rice gets crispy at the bottom (Tahdig) but doesn't burn.
(Optional) If using Cinnamon sticks to make the rice fragrant, at Step. 7 open the lid of the pot & stick the Cinnamon sticks into the rice, perpendicularly, making sure the sticks are completely submerged in the rice . Cover the pot once again tighly & allow to steam - as in Step 7 - gently for 20 minutes before serving.