In a large bowl, combine the 3 pounds beef cheeks, 4 large (12 oz) carrots, 4 stalks (7 oz) celery, 4 cloves garlic, and 1 medium (8 oz) yellow onion with the 2 teaspoons Dijon mustard, 4 fresh bay leaves or 8 dried bay leaves, 1 small pinch of ground cloves, a generous pinch of freshly ground black pepper, and the 3 cups red wine. Mix well, then cover and refrigerate overnight.
Preheat the oven to 325ºF (163°C).
Set a colander over a large bowl. Pour the contents of the beef bowl into the colander. Reserve the drained liquid. Place the 1/3 cup all-purpose flour in a medium bowl. Pick out just the beef and pat dry with paper towel, then toss with the flour.
In a large Dutch oven over medium heat, melt the 1 1/2 tablespoons (3/4 oz) unsalted butter with 2 tablespoons olive oil. Working in batches, brown the floured beef all over, turning with tongs and removing to a plate with any crispy bits once browned. Add more butter if the Dutch oven becomes dry.
Tip the vegetables into the Dutch oven, and cook until starting to caramelize, 10 to 12 minutes, stirring occasionally and scraping up any sticky bits. Return the beef to the Dutch oven, pour over the reserved wine from the marinating liquid and 3 cups boiling water, then bring to a simmer.
Cover with a scrunched-up sheet of damp parchment paper and transfer to the oven until the beef is beautifully tender, about 4 hours, topping up with splashes of water, if needed. In a large non-stick skillet over medium-high heat, combine the 6 slices smoked bacon, 7 ounces shallots, and 14 ounces button mushrooms and cook the mixture until golden, stirring regularly, 20 to 25 minutes.
Toss in the 1/2 bunch fresh flat-leaf parsley, then pour the contents of the skillet over the bourguignon and season to perfection, tasting and tweaking.