Put flour, salt, pepper, and herbs into a resealable plastic bag and shake well.
Flour beef cubes with this mixture in three or four batches.
Put a bit of oil and a little butter into a cast-iron Dutch oven.
Brown beef cubes in two or three batches. Set aside. Still using same Dutch oven, fry onions, adding a little oil if needed.
Deglaze with the red wine or balsamic vinegar with the added broth, scraping bottom of pan well to detach the browned bits.
Add the garlic, Worcestershire sauce, and Dijon mustard.
Add reserved beef to the Dutch oven, stir together, and then add the broths.
Bring to a boil and reduce heat. Simmer over low heat for 90 minutes.
Add the carrots, cover, and continue cooking over low heat for 30 minutes.
Meanwhile, fry the lardoons (or bacon) in a skillet over medium-high heat until nicely browned. Add mushrooms and leeks, and continue cooking until golden brown. Season with salt and pepper.
Transfer lardoons mixture to the Dutch oven and stir well. The meat should now shred easily.
To serve, top each serving of beef bourguignon with coarsely chopped flat parsley.
Serve with mashed potatoes or large pasta like pappardelle.