Boil potatoes with root vegetables, if using, until tender.
While potatoes cook, heat EVOO in a Dutch oven or large skillet with high sides over medium-high heat. Add bacon and crisp 2-3 minutes then add beef and brown well. Add shallots, carrot, mushrooms, bay and thyme to the pan. Cook vegetables 7-8 minutes to soften, then season with salt and pepper. Add wine to the pan and scrape up drippings, let reduce 1-2 minutes, then add in stock and Worcestershire sauce.
In a small pan, melt 2 tablespoons butter and combine with flour, whisk 1 minute then pour the roux into beef mixture. Stir to combine and thicken.
Preheat broiler with rack in center of the oven.
Drain cooked potatoes and/or root vegetables and return them to the hot pot. Mash with remaining 2 tablespoons butter, milk or half-and-half, herbs, Dijon mustard, salt and pepper. When you have reached your desired consistency, stir in the egg.
Scoop the meat into a casserole dish or individual casseroles set on a baking sheet. Top the meat with potatoes. Place under broiler, until brown.