Preheat your oven to 350 degrees.
In a large skillet or dutch oven, heat the oil. Season your beef with salt and pepper on both sides. Add beef to the skillet and cook over moderate heat, turning only once or twice, until browned and crusty, about 12-15 minutes. Transfer the beef to a separate dish and set aside.
Add the onion, carrots, celery and garlic to the skillet (with all the lovely browned bits) and cook over low heat, stirring occasionally, until very soft and lightly browned, about 15-20 minutes. Add the wine and thyme sprigs and bring to a boil over high heat.
Add the beef back in and transfer to a large, enameled cast-iron casserole or dutch oven (if you are not cooking in it already). Add the chicken stock and bring to a boil. Cover and cook in the lower third of the oven for about 1 1/2 hours, or until the meat is tender but not falling apart. Remove from oven and shred.