Place onion, celery and garlic in the crockpot.
Heat a large skillet over high heat. Season short ribs with salt and pepper. Add olive oil and, working in batches, brown short ribs on all sides then transfer to crockpot.
Pour off all but 1 tablespoon of fat. Add tomato paste and cook, stirring, until darkened, about 2 minutes. Add white wine to skillet and cook, scraping up brown bits, until reduced by half. Stir in stock and Worcestershire sauce and pour over short ribs. Tuck in rosemary, thyme and bay leaves. Cook, covered on low, for 6-8 hours or until meat is very tender.
Transfer meat to a plate and tent with foil to keep warm. Spoon fat off the cooking liquid and discard. Carefully strain cooking liquid, discarding solids, and set aside.
In a medium pot, melt 2 tablespoons butter over medium heat. Whisk in flour and cook, stirring constantly, until lightly golden brown and toasty. Slowly whisk in 1 cup of strained cooking liquid. Bring to a boil, reduce to a gentle simmer and cook, whisking often, until thickened and smooth, about 10 minutes. Taste, add more salt or pepper if needed.
Meanwhile, bring a large pot of water to a boil. Cook egg noodles according to package instructions, reserving 1 cup cooking liquid before draining. Bring reserved cooking liquid to a simmer, then whisk in remaining 1 stick butter, a piece at a time, until melted. Return pasta to the pot and cook, tossing constantly, until sauce is thick and coats the pasta.
Transfer to a large serving platter and top with short ribs. Drizzle with gravy and sprinkle with fresh thyme.