In a large Dutch oven over medium-high heat, heat the olive oil. Season the short ribs with salt and pepper, to taste, and sear in the Dutch oven until brown, about 5 minutes per side. Remove the meat from pan and set aside. Add the onions and garlic to the same pan and saute, until lightly browned. Scrape any brown bits from the bottom of the pan using a wooden spoon. Add the carrots and celery and let cook for 5 more minutes.