Preheat your oven to 300°F (150°C).

In a large Dutch oven, heat the olive oil over medium-high heat. Season the short ribs with salt and pepper, then sear them in the hot oil until browned on all sides, about 8-10 minutes. Remove the ribs and set them aside.

In the same pot, add the chopped onion and cook until softened, about 5 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.

Add the beef broth, red wine, tomato paste, thyme, and bay leaves to the pot. Stir well to combine.

Return the short ribs to the pot, ensuring they are submerged in the liquid. Cover the pot with a lid and transfer it to the preheated oven. Braise for 3 hours, or until the meat is tender and falling off the bone.

While the ribs are braising, prepare the garlic mashed potatoes. In a large pot, combine the cubed potatoes and garlic cloves. Cover with cold water and add a pinch of salt. Bring to a boil and cook until the potatoes are fork-tender, about 15-20 minutes.

Drain the potatoes and garlic, then return them to the pot. Add the milk and butter, and mash until smooth. Season with salt and pepper to taste.

Once the short ribs are done, remove them from the oven and let them rest for a few minutes. Serve the ribs over a generous scoop of garlic mashed potatoes, spooning some of the braising liquid over the top.