Wash and clean the chicken. Peel and chop the vegetables into suitably sized pieces. Wash and peel the mushrooms. Cut them into slices.
Put some of the vegetables in an oven bag, add the chicken, season with salt, paprika. Add the butter and the rest of the vegetables. Tie the bag and place it in an oven dish in the oven.
Bake for 40-45 minutes at 428°F (220 °C). If you want the chicken to be crispy on the outside, tear the bag open and finish roasting on both sides until golden. Sprinkle it with fresh rosemary.