Heat 2 tablespoons of ghee in a large, heavy-bottomed pot or Dutch oven over medium heat. Add the bay leaves, cardamom, cloves, and cinnamon; let them sizzle for 30 seconds until fragrant. Add the sliced onion and cook for 8–10 minutes, stirring often, until deep golden brown — this caramelization is the backbone of the gravy. Stir in the ginger garlic paste and cook 1 minute. Add the chopped tomatoes, turmeric, and the remaining tablespoon of ghee. Cook for 8–10 minutes until the tomatoes break down into a thick masala and you see ghee glistening at the edges. Pour in ½ cup water, add the marinated chicken with all its marinade, and simmer covered for 12–15 minutes until the chicken is nearly cooked through (165°F / 74°C internal temperature). Uncover and cook 3–4 minutes more so the gravy is thick — there should be very little free liquid, because cauliflower rice releases water as it steams.

While the chicken simmers, pulse the cauliflower florets in a food processor until they resemble rice grains — work in batches and stop before it turns to mush. (Skip this if using pre-made cauliflower rice.) Heat 2 tablespoons of ghee in a large skillet over medium-high heat. Add the cauliflower rice, salt, and turmeric; sauté for 4–5 minutes until just tender with a slight bite. Do NOT cook it fully — it will steam further during the dum. Divide the sautéed rice in half: drizzle the saffron milk over one half and toss gently for golden streaks, leaving the other half plain.

Spread the chicken masala in an even layer at the bottom of the same heavy pot, scraping in all the thick gravy. Spoon half the cauliflower rice over the masala, then scatter half the fried onions, half the mint, and half the cilantro. Spoon over the remaining cauliflower rice, alternating the plain and saffron-tinted portions for a marbled look. Finish with the rest of the fried onions, mint, cilantro, the slit green chilies if using, and drizzle the 2 tablespoons of melted ghee over the top.

Cover the pot with a tight-fitting lid. For a proper seal, place a clean kitchen towel under the lid or crimp foil around the rim before lidding. Reduce the heat to low and steam for 12–15 minutes — this is the dum. You'll smell the saffron and fried onions blooming through the steam. Resist the urge to lift the lid; the trapped steam is what marries the layers.

Turn off the heat and let the biryani rest, still covered, for 10 minutes. Remove the lid, discard the whole spices you can find, and gently fluff the top layer with a fork — scoop from the side so you lift up chicken with each serving and keep the layers visible. Garnish with extra fried onions and herbs, and serve hot.