Rinse the Basmati rice in cold water until the water runs clear. Soak the rice in water for 15 minutes, then drain and set aside.
Boil cauliflower in hot water. Set aside.
In a cooker, heat 2 tablespoons of cooking oil over medium heat. Add the cinnamon stick, cloves, green cardamom pods, and fennel seeds. Sauté for a minute or until fragrant.
Add the thinly sliced onions and sauté until they turn golden brown.
Add the ginger paste and garlic paste. Sauté for a couple of minutes until the raw smell disappears. Add the boiled cauliflower florets, diced carrots, peas, and green chillies. Sauté the vegetables for a few minutes until they are partially cooked.
Add the chopped tomatoes and cook until they become soft and the oil starts to separate.
Add the red chilli powder while cooking vegetables. Add freshly chopped mint and coriander leaves. Cook for 2 minutes.
In a small bowl, whisk the curd until smooth. Add the curd, and cook for 1 minute. Add juice of 1 lemon.
Pour the water —season with salt to taste.
Drain the soaked Basmati rice and add it to the pot. Stir well to combine the rice with the vegetables and curd mixture.
Bring the mixture to a boil, then reduce the heat to low. Cook by boiling it for 2 whistles. Vegetable Biryani is ready to garnish.
Heat 2 tablespoons of ghee in a separate pan over medium heat. Add the cashews and sauté until they turn golden brown. Set them aside. Add as garnish. The biryani is ready to serve. You can serve the biryani with onion and cucumber raita.