In a small pan, melt the butter and flour together over medium heat. Stir constantly and cook out the flour taste- about 1-2 minutes. Remove from heat and whisk in 1 cup of the veggie broth. This will make a thick slurry. Remove from pan and put into a bowl and set aside.
Season the beef generously with salt and pepper.
The stew gets most of its flavor from the browned meat, so do not use a non-stick pot for this recipe, and season and brown the meat well!
Using a dutch oven or large stock pot, heat the pot over medium high heat. Add olive oil and throw in veggies. Stir CONSTANTLY and cook for about 3 minutes. Remove veggies from pan and set aside. Add a little more oil and return pan to heat.
Add the beef in a single layer (do it in 2-3 batches if necessary) and brown all sides, about minutes 5 minutes per batch. Add a little more olive oil as needed for each batch.
Remove the beef from the pan, and set aside in a bowl. Pour the cider vinegar into the pot. (this will create quite a pungent steam, so look out and breathe with caution) Using a wooden spoon, quickly scrape up all the brown bits from the bottom of the pot.
Return all the beef to the pot. Add all the veggies and the broths. After cooking for about 45 minutes, take some of the broth (about 1/2 cup or so) from the stew and add it to the bowl with the slurry- stir until mixed and slowly add the slurry to the stew. Stir until combined and then add the barley.
Cover and continue cooking.
Check on and stir the stew every 20 minutes or so.
Bring to a boil, reduce heat to very low, and simmer, covered, until the beef is very tender 1-1/2 to 2 hours.
In a small bowl, mix 1/3 cup of the stew liquid with the corn starch and stir until smooth. Add to the stew and stir. It should thicken slightly. You don't want it too thick, so don't use more than 2 teaspoons of corn starch.
Continue to simmer over low heat and allow the broth to thicken, about 3-5 minutes. Taste and adjust seasonings to your desired tastes- I normally need to add about 1 teaspoon of kosher salt and 1/2 teaspoon of black pepper. Add the parsley.
Spoon into bowls and serve with some warm ciabatta bread or rolls.
Stew will thicken over time- but in this recipe the gravy will be a bit thin compared to a canned beef stew. Feel free to add more rue if necessary. I prefer that my meat and veggies not compete with a thick, overly rich gravy.
