Clean the onion, chop it and stew it along with the grated carrot until soft. Add the finely chopped spinach, sprinkle it with salt and pepper. Slightly tenderize the chicken breasts in a plastic bag and salt them. On top of a greased surface or foil, distribute the meat so as to get something like a rectangle.
Overlap the individual chicken pieces with each other. Spread vegetables over the meat, sprinkle with crumbled feta cheese and gently roll it up, using the foil to help you. Tie the chicken roll with thread so it doesn't fall apart when baking. Or you can pinch it with toothpicks.
Put it into a greased pan with wine, smear it with butter thoroughly and put it to bake under foil for about 30 minutes. Remove the foil and let it get a slight tan. Serve garnished with fresh steamed potatoes.