Season the flour with salt and pepper to taste. Toss the veal shank slices with the flour until evenly coated. Melt the butter and olive oil in a large skillet over medium heat. Cook the shank slices in the hot butter until golden brown on all sides, about 10 minutes per side.
Step 2
Combine the onions, carrots, celery, and garlic in a large slow cooker. Set the meat slices atop the vegetables, then pour in the chicken stock and diced tomatoes. Season with oregano and the bay leaf.
Step 3
Cook on Low for 8 hours until the meat is falling off of the bone. Season to taste with salt and pepper before serving.