Wash the chicken and season inside and out with salt and pepper. Peel and roughly dice the onions. Wash the sage and dab dry. Coarsely chop half of the sage, mix with half of the onions and add to the chicken.
Place the chicken in a large roasting pan or a fat pan of the oven. Pour on 1/8 litre of broth. Roast in the preheated oven (electric cooker: 200 °C/ gas: level 3) for 1-11/4 hours. Clean and wash the carrots and courgettes and cut them into thick slices.
After 20-30 minutes, cover the chicken with bacon and remaining sage. Spread vegetables, remaining onions and broth around the chicken and season with salt and pepper. Finish frying, turning the vegetables from time to time.
Peel the garlic, press it through a garlic press and mix with yoghurt and lemon peel. Season to taste with lemon juice, salt and pepper. Arrange chicken and vegetables on a plate and serve with yoghurt sauce.