Preheat the oven to 300 degrees.
Heat 1 tablespoon of oil over medium-high heat in a braiser that is oven-safe.
Cooking in batches, sear the pieces of beef on all sides. Remove the pieces to a bowl as each batch gets a good sear. Add another tablespoon of oil to the braiser and repeat searing.
Once all the beef has been seared, add the garlic and stir constantly for about 30 seconds.
Add the tomato paste and stir, cooking until it has darkened in color.
Add the Worcestershire and balsamic, 5 cups of the stock, oregano, rosemary, thyme, and bay leaf. Season with salt and pepper as needed. Stir well.
Add the beef and any juices collected in the bowl into the braiser. Stir.
Place the lid on the braiser and put in the oven for 2 hours.
Remove the braiser from the oven. Add the peas, onions, carrots, and potatoes.
In a 2-cup measuring cup, mix 1 cup of the beef stock and the cornstarch until the starch is dissolved. Add to the stew and stir well.
Place the lid on the braiser and put it back in the oven for 1 more hour.
Remove the braiser from the oven and check the carrots and potatoes for doneness and the liquid for thickening. If the vegetables require more time, cook for another 20 to 30 minutes.
Remove the stew from the oven, stir, taste for seasoning and adjust as desired.
Top with parsley and serve very warm with toasted baguette slices.