Preheat the oven to 425 degrees F.

Place  Short Ribs on a sheet pan, brush the tops with olive oil, and sprinkle with ½ tablespoon salt and ¾ teaspoon pepper. Roast for 20 minutes, then remove from the oven. Reduce the temperature to 325 degrees F.

Meanwhile, heat 1/4 cup olive oil in a large Dutch oven, over medium high heat. Add the celery, onions, and carrots and cook until tender, about 15 minutes, stirring occasionally. Add the garlic and cook for one minute. Add the wine, bring to a boil, lower the heat, and simmer for a few minutes.  Add the stock, tomatoes, Stout beer, thyme, ½ tablespoon salt, and ¾ teaspoons pepper.

Place the Short Ribs in the pot. Bring to a boil, cover, and cook in the oven for 1½  to 2 hours. Uncover and cook for one more hour, until the meat is very tender.

Remove the Short Ribs to a plate with a slotted spoon and discard the thyme bundle and bones. Simmer the sauce on the stove for 10 minutes. Skim the fat off the top and discard. Return the ribs to the pot, heat for 5 minutes, and taste for seasonings. Serve with garlic mashed potatoes and a garnish of fresh thyme sprinkled on top.