Preheat oven to 300f and move racks to make enough room to accommodate a large Dutch oven pot in the middle of the oven.
Pat the short ribs dry and season with 2 teaspoons kosher salt and a ½ teaspoon of black pepper on all sides. Heat a large Dutch oven to medium heat. After the pot is hot add the olive oil. Give the short ribs one more pat to make sure they're dry, then add them to the pot and and sear on all sides. Work in batches and do not crowd the pan. Short ribs should take about 10 minutes to sear on all sides per batch.
Set the seared short ribs aside and turn the heat down to medium-low. Add in the carrots, and onions and saute in the beef fat until very soft (about 10 minutes) then add the garlic and cook for 2 minutes longer.
Next, add in the tomato paste and cook for 3 minutes stirring frequently. Add the wine and turn heat to medium. Using a wooden spoon scrape all the brown bits off the bottom of the pan.
After cooking the wine for 3 minutes, add the plum tomatoes, thyme, and bay leaf and bring to a simmer. Once simmering add the short ribs to the pot, stir, then turn off and cover. Cook short ribs in the oven for 2 hours. After two hours, place the lid partially ajar and continue to cook for 1 more hour.
Remove Dutch oven, then remove short ribs and place onto a large cutting board. Using 2 forks, shred the meat. Discard any hard parts of fat and the bones. Also, discard any thyme stems and the bay leaf. Return the shredded meat to the pot and keep warm over low heat. Taste test the ragu and season with salt and pepper to taste.
Bring a large pot of salted water (2 tablespoons kosher salt) and cook pappardelle until al dente. Heat a large pan to medium-low heat and add in 2 cups of the short rib ragu. Add the al dente pasta to the pan and cook for 1 more minute mixing well to thoroughly coat the pasta.
If the pasta needs more ragu, add more now. If the sauce seems a little dry add a bit of reserved pasta water to loosen it up. Serve plated with grated Parmigiano Reggiano and the remaining ragu on the side. Enjoy!