Arrange a rack in the middle position and heat the oven to 425 degrees.

In a medium bowl, combine the chicken with ⅓ cup coconut milk, 1 teaspoon garam masala, 1 teaspoon salt and ½ teaspoon pepper. Toss to coat and set aside to marinate.

In a blender, combine the spinach, scallions, cilantro and serrano chile. Pour in the chicken broth and remaining coconut milk and blend until smooth. Season the spinach purée to taste with salt and set aside.

Heat a large (12-inch) ovenproof skillet or wide braising pan with a lid over medium-high. Once hot, add the olive oil and arrange the chicken in a single layer, skin side down. Cook for 6 to 8 minutes, until the skin on the bottom is a deep golden brown. Turn and cook for another 3 minutes, until the chicken is lightly browned and releases easily from the pan. Set chicken aside on a plate, skin side up.

Lower the heat to medium. If the pan looks dry, add more oil to coat the bottom of the pan. Add the garlic, ginger and remaining 2 teaspoons garam masala. Cook, stirring constantly to make sure the garlic and spices don't burn, until garlic is fragrant, 1 to 2 minutes. Add the rice and stir until the rice turns opaque, 2 minutes more.

Pour in the spinach purée, scraping the bottom of the pan with your cooking spoon to release any browned bits. Bring the liquid to a simmer and cook for 5 minutes, stirring often. Turn off the heat and arrange the chicken in the pan, skin side up (along with any accumulated juices). Place a piece of foil on top, then cover the pan with a lid, transfer to the oven and bake for 20 minutes, until the chicken is cooked through and the rice is tender.

Remove the pan from the oven and transfer the chicken to a plate. Add the thawed peas (if using) and the juice of half the lime. Taste, adding more salt and lime juice if needed, and fluff the rice with a fork. Cover the pan and let steam for 10 minutes before serving. If desired, place the chicken on a sheet pan under the broiler for 2 to 3 minutes to crisp up the skin.

Serve chicken and rice straight from the pan, garnished with lime wedges and more cilantro leaves.