Preheat the oven to 180 °C. Cut the onion lengthwise and slice thinly. Also slice the garlic and mushrooms thinly. Dice the tomatoes into small cubes.

Cut the chicken into individual pieces - cut off the thighs and cut them at the joint into 2 parts. Cut off the wings and separate the wingtips. Cut off the breasts and divide them into 2 equal parts. Season the meat thoroughly with salt and pepper on all sides. Use the chicken carcass and wingtips to prepare broth for another dish.

In a large pot, heat oil over high heat and sear the meat, skin-side down, for 3 minutes until golden. Reduce heat by half, turn the meat, and cook for another 3 minutes.