Salt and pepper the chicken breasts. Clean the mushrooms and cut them into pieces. Peel the garlic and cut into slices. Wash the thyme, shake it dry and pluck it from the stem.
Mix mushrooms, garlic, thyme, white wine, Rama Cremefine for cooking and cornstarch in a bowl, add salt and pepper.
Double aluminum foil (30×50 cm), put mushroom mixture in the center, place chicken breasts on top and close the aluminum foil to form a packet. Cook on a baking tray in a preheated oven at 225°C (gas: level 4/circulating air: 200°C) for 45 minutes.