Rinse the basmati rice thoroughly under cold water until the water runs clear, then soak in water for 15 minutes.
While the rice soaks, peel and dice the potatoes into bite-sized pieces.
Drain the soaked rice and set aside. In a large pot, heat vegetable oil over medium heat and add cumin seeds. Wait for them to sizzle and release aroma.
Add finely chopped onion to the pot and sauté until translucent and fragrant, about 3-4 minutes. Stir occasionally to prevent sticking.
Push the onions to one side of the pot, then add minced garlic and grated ginger to the cleared space. Cook for about 30 seconds until fragrant.
Add ground turmeric, garam masala, cinnamon, and cardamom to the pot. Stir well to coat the onions and spices until they become fragrant—about 1 minute.
Add diced potatoes to the pot, stir to coat with the spices, and cook for 2-3 minutes, allowing them to absorb flavors and start to soften slightly.
In a small bowl, steep saffron threads in 2 tablespoons of hot water until the water takes on a golden hue, about 5 minutes.
Add the drained rice to the pot, gently mixing with the potatoes and spices. Pour in water, add salt to taste, and bring to a boil. Once boiling, reduce heat to low and cover tightly.
Drizzle the infused saffron water over the rice, spreading it evenly for a vibrant color and fragrant flavor. Let the rice simmer on low for 15-20 minutes until the water is absorbed and rice is fluffy.
Turn off the heat and let the biryani sit, covered, for 5 minutes to allow flavors to meld and steam to finish the cooking process.
Gently fluff the potato biryani with a fork, then serve hot, allowing the fragrant spices, tender potatoes, and fluffy rice to shine.
