Preheat the oven to 350°F. Lie a plate with paper towels. Heat a large skillet over medium high heat. Add the bacon and sauté until just crisp, about 8 minutes. Transfer the bacon to the paper towel-lined plate and pour off the excess fat.
Meanwhile, slice the potatoes about ¼-inch thick.
Return the skillet to medium meat. Add the oil and then add the onions and leeks and sauté until very lightly browned and softened, about 10 minutes. Add the mushrooms and turn the heat up to medium-high. Sauté for about 8 minutes, until the mushrooms are tender and golden brown and any liquid that was released has evaporated. Add the garlic and stir for one minute until the garlic becomes fragrant. Pour in the white wine and scrape up any bits stuck to the bottom of the pan. Allow the wine to mostly evaporate, then add the broth, cream and parsley and bring to a simmer.
Place 1/3 of the potatoes in a Dutch oven or other heavy ovenproof pot with a lid. Spoon over about 1/3 of the mushroom leek mixture from the skillet. Sprinkle over 1/3 of the bacon. Layer another 1/3 of the potatoes on top, then spoon over another 1/3 of the mushrooms and leeks, another 1/3 of the bacon. Layer over the rest of the potatoes, sprinkle over the rest of the mushrooms and leeks, then pour over the remaining cream mixture. Finish with the rest of the bacon. Cover the pot and bake for about 1 hour, gently stirring the vegetables at 20 minutes and 40 minutes, then letting them cook an additional 20 minutes or so, until the potatoes are tender. When the potatoes are cooked, remove the pot from the oven, sprinkle over the cheese, and replace the lid. Let sit for 5 to 10 minutes until the cheese is melted and serve. Scoop down to get the potatoes and the bottom, and make sure there is some cheese with each serving.