Add chicken, onion, garlic, bay leaf, peppercorns, and salt to a large pot. Cover with water by about 1 inch.
Bring to a gentle boil, then simmer 25–30 minutes until the chicken turns tender and nearly cooked through.
Remove chicken to a tray. Strain and reserve the broth. Skim excess fat if you like.
Pat chicken dry and sprinkle with half the spice blend and a pinch of salt. Set aside.
Rinse and soak the rice 20–30 minutes; drain well.
Brush eggplant, potatoes, carrots, and cauliflower with oil and season with salt.
Pan-fry or roast at 425°F (220°C) until golden and just tender: eggplant 15–20 minutes, potatoes 20–25, carrots 12–15, cauliflower 12–15. You want color without overcooking.
Tomato slices don’t need pre-cooking; keep them raw.
Heat a spoon of oil in a wide skillet. Sear the seasoned chicken on both sides until lightly browned, 3–4 minutes per side. This boosts flavor and texture.
Choose a heavy 5–6 quart pot with straight sides and a tight lid. Line the bottom with a circle of parchment to help with the flip.
Layer in this order (bottom to top): tomato slices, potatoes, eggplant, carrots, cauliflower, then chicken.
Sprinkle the remaining spice blend over the chicken and vegetables.
Top with drained rice, smoothing it into an even layer. Do not pack it down.
Mix saffron water into 2 to 2 1/2 cups hot broth, then pour gently over the back of a spoon to avoid disturbing layers. The liquid should barely cover the rice; adjust as needed.
Taste the broth on top and adjust salt. The liquid should taste well-seasoned and flavorful.
Bring the pot to a mild simmer over medium heat until you see small steam vents in the rice, about 5–7 minutes.
Cover tightly. Reduce heat to low and cook 15 minutes.
Transfer the covered pot to a 350°F (175°C) oven and bake 20 minutes more. This ensures even heat throughout.
Remove from oven and let the pot rest, still covered, 10–15 minutes. Resting sets the layers and keeps the flip intact.
Run a thin spatula around the pot edges. Place a large, rimmed platter over the pot. Using oven mitts, grip and flip confidently in one motion.
Lift the pot slowly to reveal the layered dome. Peel away the parchment. Garnish with herbs and toasted nuts.
