In a Dutch oven or large, heavy pot, heat the oil over medium-high heat. Add the onions, bell peppers, and celery, and cook, stirring, until they begin to caramelize, about 5 minutes. Add the garlic and cook, stirring, for 30 seconds. Add the tomato paste, stir well to combine, and cook until it begins to brown, about 1 1/2 minutes. Add the red wine and cook, stirring, to deglaze the pan and loosen any bits clinging to the bottom. Add the ham hocks and veal stock, and bring to a boil. Reduce the heat to medium and simmer until reduced by half, 2 hours and 45 minutes. Remove from the heat. Remove the ham hocks and set aside to cool.
Meanwhile, in a small saucepan, melt the butter over medium heat. Add the flour, whisking constantly, until smooth and starting to thicken, about 2 minutes. Continue to cook, constantly stirring with a wooden spoon until the roux has a nutty aroma and becomes a light peanut butter color, 3 to 4 minutes. Remove from the heat and cool.
Whisk the cooled roux into the hot gravy and bring to a boil. Reduce the heat to medium-low and simmer for 5 minutes until thickened. Cover to keep warm.
Remove the fat and skin from the ham hocks and discard. Remove the meat from the bone and finely chop. Return the meat to the gravy, add salt and pepper to taste, and keep covered until ready to serve with the stuffed pork chops.
Yield: 2 cups