Preheat oven to 350°. Pat stew meat dry with paper towels.
In an oven-safe Dutch oven on medium heat on the stove top, cook the chopped bacon until crispy, then remove. Pour off all but about 2 Tablespoons of bacon fat.
Heat the bacon fat in the Dutch oven on medium high heat. Sprinkle the meat liberally with salt and pepper and sear it in batches in the bacon fat. Don't crowd the pan. Turn the meat chunks over as they become nicely browned. Remove.
Sauté the onion and celery on medium heat in the Dutch oven for about 5 minutes. Don't brown them. Add the garlic, red pepper flakes and flour and stir. Whisk in the beer, stock, vinegar and brown sugar, scraping up the brown bits crusted on the pan as you whisk. Add the thyme, salt and pepper.
Return the meat and bacon to the pot. Add in the mushrooms, carrots and potatoes. Bring to a boil for just a minute to ensure you're placing hot stew into the oven.
Cover the pot and place it in the oven for 1½ hours. You may need to remove an upper rack to easily fit the pot in the oven.
Remove the pot and taste the meat. If it's tender, it's ready. If it's still a little tough and chewy, return to the oven in 15 minute increments. Adjust the salt and pepper seasoning while you're tasting.
Serve with a salad and/or bread or muffins.