Preheat oven to 375 degrees Fahrenheit. Dry veal pieces with paper towel and season on all sides with salt and pepper.
Heat grapeseed oil in heavy oven-ready pot or Dutch oven. When the oil is hot and begins to smoke add a layer of veal. Do not crowd the pot. Brown all sides over moderate heat. When first batch is browned, remove and reserve. Add second batch and repeat. Add more oil if needed. Remove the veal and reserve.
In the same pot, add mushrooms to the pan. Brown quickly and cook off the water content of the mushrooms. Remove and reserve.
Add the pearl onions to the same pot, adding more grapeseed oil if needed and cook until golden brown on all sides. Remove from pan.
Pour oil from pot leaving about 2 tablespoons. Melt the unsalted butter in the pot and return all the browned veal to the pot. Sprinkle veal with flour and reduce the heat. Cook over low-to-medium heat while stirring until flour is absorbed.
Increase the heat to high and deglaze the pot with veal or beef stock and be sure to scrape up the browned bits, the fond. Add the white wine, tomatoes, shallots, garlic, thyme, bay leaves, pearl onions, mushrooms and stir. Cover with water if needed.
Cover with a lid and cook in the oven at 375 degrees for 45 minutes.
Serve and garnish with chopped parsley as needed.