Pat beef chunks dry and season with salt and pepper.
Heat heavy dutch oven over medium heat on the stovetop. Add bacon fat or oil. Sear chunks of beef in small batches to caramelize, turning often. Remove to plate between batches. Peel and slice garlic cloves. Saute along with last batch of beef.
Return all cooked beef to the pot. Sprinkle flour over top and stir until all meat is coated. Add red wine and beef broth. Cover and simmer on low heat while you prep the vegetables.
Peel pearl onions. Clean and quarter or half mushrooms. Peel and chop carrots into bite sized pieces. Add to pot of beef.
Prepare a Bouquet Garni by arranging a few sprigs of rosemary, thyme and parsley and tie with butcher twine or cotton thread. If using a fresh bay leaf, wrap around the bouquet under the string. Otherwise toss dry bay leaf in pot along with herbs.
Place in the oven at 350 degrees and bake for about an hour. Check and stir. Return to oven and bake an additional hour, up to 2 more hours until the stew is dark and reduced.
Cool and refrigerate unless you are serving it immediately.
Meanwhile, prepare garlic mashed potatoes. Peel and boil potatoes in salted water until fork tender. Trim top off garlic head to expose most of the cloves. Drizzle with olive oil, wrap in foil and roast in oven for 30-40 minutes until cloves are very soft and golden.
Drain potatoes, add milk, butter and salt. Squeeze garlic into potato mixture. Whip or mash to desired consistency.
Serve Beef Bourguignon over garlic mashed potatoes.
Garnish with fresh parsley and cracked black pepper if desired.