Marinate the meat in the Mustard and White Wine Marinade for an hour at room temperature or covered overnight in the fridge. A 9-inch square glass casserole works well for this. If there isn’t enough liquid to come to the top of the meat, add a little more wine.
Remove meat from the marinade ¬— reserving marinade — to a plate lined with paper towels, and adding another layer of paper towels on top, pat the meat dry. Heat olive oil over medium flame in a large, deep skillet. When hot, add half of the elk in an even, spaced layer. Brown, turn, cook the other side, and remove to a bowl. Repeat with the rest of the meat, adding a little oil if you need to. When you turn the last of the meat, add the leeks and onions, and cook 4-5 minutes. Return the cooked meat from the bowl into the pan, stir, and sprinkle with flour. Cook, stirring, two or three minutes, and pour in reserved marinade. Simmer another two or three minutes, scraping the bottom of the pan. Carefully pour or spoon the meat and vegetable mixture with the cooked marinade into a 6-quart slow cooker.
Add the wine to the skillet and heat through, scraping the bottom of the pan once more, and simmering a few minutes until reduced a bit. Pour the wine into the slow cooker on top of the meat and vegetables. Stir in the elk or other broth. Add the carrots, potatoes, rutabaga, turnips, parsnips, tomato paste, bay leaves, thyme, and rosemary. Stir well. Taste and adjust salt if needed. At this point, the stew should still be fairly brothy. If it appears thick, add another cup of broth or water. It will thicken as it cooks.
Set slow cooker to cook on low for 8 hours, stirring once halfway through cooking if possible.
If serving that night, add cooked bacon and mushrooms for the last 30 minutes of the cooking time. Taste and add salt and/or pepper as needed. Serve hot garnished with minced parsley and/or scallions.
If serving the next night: Cool, carefully pour into an 8-quart soup pot, and store covered in the fridge overnight. The next night, add cooked bacon and mushrooms, heat slowly over medium-low flame, stirring regularly until hot and bubbling. Serve hot garnished with minced parsley and/or scallions.
Leftovers will keep in the refrigerator for 3-4 days tightly covered or in the freezer for 4 months.