This is my riff on yassa, a traditional Senegalese dish of chicken or other meat and onions marinated in a tart mixture of vinegar, citrus, chiles and spices. The flavors are entrancing, and it's a knockout for a dinner party. The chicken and most of the ingredients can marinate overnight, and the marinade becomes the sauce for the finished dish, so most of your prep is done ahead. Here I braise the chicken, making it a one-pot dish and an excellent choice if you want a spectacular dinner without a lot of hassle (or clean-up!).
Whisk together the vinegar, lemon juice, garlic, ginger, mustard, lemon zest, chile, black pepper, cayenne and salt to taste in a large nonreactive bowl or other container. Stir in the onions and bay leaf. Add the chicken to the marinade and toss to coat. Refrigerate, covered, turning the chicken in the marinade if it's not completely covered, at least 6 hours or overnight.
Heat the oil in a large Dutch oven or heavy pot over medium-high heat. Remove the chicken from the marinade; reserve the marinade. Working in batches to avoid overcrowding the pot, add the chicken to the pot and sear until golden brown on both sides, about 8 minutes. Transfer the chicken to a plate and set aside.
Add the allspice to the pot and cook until fragrant, about 1 minute. Spoon the solids from the marinade into the pot and cook, stirring, until softened, about 5 minutes. Add the reserved liquid and chicken, making sure to spoon the sauce over the chicken to coat. Add about 1 cup of water to the pot. Cover and cook over medium heat until the chicken is cooked through, about 30 minutes. Discard the bay leaf.
Place the chicken on a serving platter. Spoon the onions and sauce from the pan over the chicken. (Simmer the sauce, uncovered, for 5 minutes on medium heat if there is too much liquid; it should be a rich sauce.) Season with salt and pepper and serve with the rice.