Cut a pocket in the chicken breast. Fill the chicken breast with tomato and mozzarella.
Cut the onions into small cubes and sauté in the oil. Add the cream and bring to the boil. Season to taste with salt, pepper and marjoram. Thicken with cornstarch. Add a few leaves of basil. Then puree the sauce with a blender.
Sear the chicken breast on both sides and then cook in the pan for a few minutes. Then continue cooking in the oven at 120 ° C for about 12 minutes.
Cook gnocchi (unless you have fresh ones from the refrigerator). Fry in a pan with butter until golden. Add the finely chopped herbs to taste and season with salt and pepper.