How to Make It
Season the beef shin with salt and pepper. In a very large skillet, heat the vegetable oil until shimmering. Add the beef shin and cook over high heat until browned all over, about 10 minutes total. Transfer the beef shin pieces to a slow cooker. Pour the wine and 2 cups of the water into the skillet and bring to a boil, scraping up the browned bits from the bottom of the pan; pour the liquid into the slow cooker.
Add the remaining 8 cups of water to the slow cooker along with the onion, carrot, celery, parsley, thyme, bay leaf and peppercorns. Cover and cook on high until the broth is very flavorful, about 6 hours. Remove the beef shin pieces and reserve for a later use. Strain the broth into a large bowl and skim the fat from the surface. Season the broth with salt. Let cool, then cover and refrigerate.