To marinade the meat add all marinade ingredients to a large bowl. Mix well and cover, refrigerate overnight, or up to 2 days.

To a Dutch oven (or other heavy oven-safe pot), heat the vegetable oil over medium heat. Remove meat from the refrigerator, and with a slotted spoon carefully add the meat to the oil, saving the marinade for later. Brown the meat, searing each side, and add the pepper while cooking. Place the cooked browned meat in a bowl and set aside. Leave any juice in the bottom of the Dutch oven.

To the Dutch oven, add the wine marinade, water, the spice sachet, the demi glace, onions, and mushrooms. Boil down for about 20 minutes until has reduced. Add the browned meat back to the pot, add half of the butter (3 tablespoons) and cover with a lid. Place the pot in the Dutch oven for 1 hour until the meat is fork tender and falls apart.

Transfer the pot back to the stove top. In a separate sauce pan, melt the remaining unsalted butter (3 tablespoons) and stir in the flour to make a roux. Slowly whisk the roux into the Dutch oven sauce, and continue stirring until the sauce thickens.

Serve with mashed potatoes and enjoy!