In a large Dutch Oven or pot, over medium-high heat, heat the oil. Add the bacon and cook until cooked through, about 4-5 minutes. Remove with a slotted spoon and reserve.
Season the beef generously with salt and pepper. Working in batches so not to overcrowd the pot, brown the beef pieces on all sides, about 1-2 min per side. Remove and reserve with the bacon.
Turn the heat down to medium. If necessary, add a little more oil. Stir in the onions and sauté until beginning to brown, about 5 minutes. Add the garlic and cook until fragrant.
Stir in the flour and tomato paste, mixing until well combined. Cook for a minute or two, until the paste turns a dark red color. Then, pour in the beer, using a wooden spoon to scrape all the browned bits from the bottom of the pot.
Stir in the beef broth, brown sugar, Worcestershire sauce, and a pinch of salt and pepper. Add the beef and bacon back into the pot, plus the thyme sprigs. Bring to a boil.
Once boiling, cover and lower the heat to a simmer. Cook for 1 hour.
Add the carrots and potatoes. Cover and continue cooking until the beef is falling-apart tender and the veggies are cooked, about 1 more hour.
If, by this point, the stew is not thickened to the desired consistency, raise the heat to medium-high and bring to a boil. Let it cook, uncovered, until thickened. You can also add a slurry of equal parts flour and cold liquid (water, beer or broth) to thicken even further.
Discard the thyme sprigs and taste for seasoning, adjusting salt and pepper if necessary.
Stir in the chopped parsley and serve!