Preheat the oven to 350 degrees Fahrenheit.
Trim off and discard excess fat from short ribs. Sprinkle both sides with salt and freshly ground white pepper.
Heat vegetable oil in a couple of large fry pans on medium-high heat. Sear ribs for 5 to 7 minutes, or until brown on all sides. Transfer to a plate and set aside. Pour off all but 1 tablespoon fat and decrease the heat to medium. Add onions and carrots; cook for about 4 minutes or until caramelized. Remove from pan. Add port and wine; stir to deglaze the bottom of the pan. Add stock, thyme, sage, browned ribs, caramelized onions and carrots to a large roasting pan. Add port and wine. Cover the top of the roasting pan with aluminum foil and with a small knife pierce 6 holes in foil to allow steam to escape.
Place the roasting pan in the oven and bake, turning meat occasionally, for 3 to 4 hours, or until meat is falling off the bone. Remove from the oven and allow short ribs to cool in liquid for 1 hour. Take meat off bones. Discard bones and keep meat warm.