Preheat Dutch oven over med-high heat for 5 minutes.
Meanwhile, pat short ribs very dry with paper towel. Season all sides with kosher salt.
Add avocado oil to preheated Dutch oven, raise heat to high and brown all sides of the short rib. Transfer browned meat to bowl and set aside.
Add onion, celery and carrot - season with a pinch of kosher salt. Sautée vegetables until softened (approximately 10-12 minutes). Be sure to scrape all the brown bits off the bottom of the pot.
Add garlic, cook an additional 60 seconds.
Return browned meat to pot, add tomato passata, thyme, and bay leaves. Season with freshly-cracked black pepper, stir to combine, bring sauce to a simmer, reduce heat to low, cover with a lid and cook 2.5-3 hours or until meat is fall-apart tender.
Transfer meat to a bowl and shred with two forks. Discard thyme stems and bay leaves.
Return shredded meat to pot, add torn basil leaves and stir to combine. Taste for seasoning and adjust salt and pepper as required. Note: If ragu has reduced too much, simply add a little bit of stock to reconstitute.
Serve overtop of cauliflower purée, mashed potatoes, or zucchini noodles.