Heat the olive oil and butter in a pan and braise the onions and celery for 5 min. Pour the flour in a plate and season with salt and black pepper. Roll the veal in it and braise them on both sides.
Pour in the wine and broth and bring to a boil, stir and lower the heat. Saute for 85 min.
In the meantime, make the gremolata, by mixing all the ingredients for it. Transfer the veal to a serving plate.
Bring the sauce in which you've sauteed the butter to a boil and let it become reduced. Pour it over the meat, sprinkle with the gremolata and serve.