Salt and pepper the chicken fillets and season with herbs of your choice.
Fry the meat in olive oil in a pan on both sides, then remove from the pan.
Briefly fry the onion cubes in the frying stock, then deglaze with balsamic vinegar and reduce a little. Pour white wine on top and bring to the boil, then add a little chicken stock.
Return the chicken fillets to the pan and simmer open for approx. 10 - 15 minutes (depending on the thickness of the fillets) over medium heat to finish cooking the meat and reduce the sauce.
Season the sauce to taste and, only if necessary, add a little more chicken stock.
The good quality of the balsamic vinegar is important because it makes the sauce thick and creamy. Please do not use a sour, cheap balsamic vinegar of inferior quality, but a round balsamic vinegar with a balanced sweetness and acidity. If the sauce is too thin, thicken it with a little flour butter.
The sauce becomes quite dark with the balsamic vinegar, but I think it looks very nice with light-colored chicken. I just put the fillets in the sauce without turning them to keep one side light.
I also like basmati rice and colorful roasted vegetables.