- With the rack in the bottom position, preheat the oven to 190°C (375°F).
- Using a knife, cut the top off the pumpkin (as if carving a jack-o’-lantern). Set aside. Using a large spoon, scoop out the seeds and loose pulp, scraping until the inside of the pumpkin is smooth. Season the inside generously with salt and pepper. Spread the rice inside the pumpkin. Place it on a large rimmed baking sheet or in a roasting pan with high sides (see note). Check to make sure the pumpkin fits easily in the oven. Set aside.
- In a large skillet over medium-high heat, brown the chicken in the oil. Season with salt and pepper. Place the chicken on the rice in the pumpkin, breast side up. Set aside.
- In the same skillet over medium heat, soften the vegetables for 4 or 5 minutes. Add oil if necessary. Season with salt and pepper. Add the wine, herbs and nutmeg. Bring to a boil and reduce until almost dry. Pour over the chicken. Close the pumpkin by setting the top in place. Wrap the stem with aluminum foil. Oil the outside of the pumpkin. Bake until the chicken and the rice are cooked, about 2 hours, 40 minutes (depending on the size of the pumpkin). Adjust the seasoning.
- Transfer the pumpkin to a serving platter by carefully lifting it with two large, stiff spatulas. Ask for help if necessary.