Preheat your oven to 200°C (400°F). Toss the mixed vegetables with 2 tablespoons of vegetable oil and a pinch of salt. Spread them on a baking tray and roast for 20–25 minutes until tender and slightly caramelized.
Rinse the basmati rice under cold water until the water runs clear. Soak it in water for 20 minutes, then drain. In a large pot, bring 1.2 liters of water to a boil. Add the soaked rice and cook for 8–10 minutes until it's about 70% cooked. Drain and set aside.
In the same pot, add 2 tablespoons of vegetable oil and heat over medium. Add the thinly sliced onions and sauté until golden brown, about 10–12 minutes. Reserve half for garnish.
Stir in the ginger-garlic paste, green chilies, and biryani masala with the sautéed onions. Cook for another 2–3 minutes until the spices are fragrant.
Lower the heat and layer half of the partially cooked rice over the spice mixture. Add half the chopped coriander and mint. Follow with the roasted vegetables and then the remaining rice. Finish with the remaining herbs and fried onions.
Drizzle 4 tablespoons of water over the top of the rice. Cover the pot with a tight-fitting lid and cook on low heat for 20–25 minutes, allowing the flavors to meld and the rice to finish cooking.
Once done, gently fluff the biryani with a fork, being careful not to break the rice grains. Serve warm, garnished with fried onions and lemon wedges on the side.
