Season the slices of chicken breasts with garlic powder, salt and pepper. Put olive oil in skillet and slowly lay the meat slices in. Cook on medium heat until the breasts get red color. Set aside, on the plate. Add butter in the same skillet and cook the onion (cut in small pieces). Stir it occasionally and let the onions cook on the lowered heat for 15 minutes. Add thyme, red pepper flakes, balsamic vinegar, grab a whisk and pour the chicken broth while whisking. Put the heat on high and cook until it thickens a bit. Add the cream and let it simmer for a few moments. Put the breasts back into the skillet and spoon the sauce on the top. Serve immediately with fresh parsley.