Make the filling. Heat vegetable oil in a frying pan. Fry mushrooms and onions. Cool and mix with cream cheese. Add salt and pepper.
Prepare the chicken roll. Place the breast fillet on a cutting board and salt. Spread the filling over the entire surface. Roll into a roll. If necessary, secure the ends with toothpicks. Preheat the oven to 180℃. Wrap the chicken breast roll in foil and place in a baking dish. Place in the oven. Bake for 60 minutes.