Cut the uncooked bacon crosswise into 1-inch wide strips to create lardons. Heat a large pan over medium heat. Add the bacon lardons to the pan in a single layer. Cook, stirring occasionally, until the bacon is crispy, about 10 minutes.
4 strips Bacon
While the bacon cooks, prepare the leeks. Trim off the dark green tops and root ends, keeping the white and light green parts. Slice the leeks thinly into rounds, or for smaller pieces, first cut the leeks lengthwise, then slice into half-moons. Rinse thoroughly under cold water to remove any dirt or grit, and set aside.
Once the bacon is cooked, transfer to a paper towel-lined plate to drain. Remove the bacon fat, but leave about 1 tbsp in the pan.
In the same skillet with the reserved bacon fat, add the sliced leeks and chopped shallot. Season with salt and pepper. Sauté over medium heat, stirring occasionally, until the leeks are softened and beginning to brown, about 5-7 minutes.
2 Leeks, 1 small Shallot, 1/4 teaspoon Kosher Salt, 1/4 teaspoon Black Pepper
Pour in the white wine or broth to deglaze the pan. Stir, scraping up any browned bits from the bottom of the skillet, and cook for 2-3 minutes until the wine has mostly absorbed.
1/4 cup Dry White Wine
Reduce the heat to low and stir in 3/4 cup of heavy cream. Allow the mixture to simmer gently for 3-5 minutes, stirring occasionally, until the sauce thickens slightly. Season with salt and pepper to taste.
3/4 cup Heavy Cream
Meanwhile, cook your pasta according to package instructions until al dente. Drain the pasta, reserving 1 cup of the cooking water. Add the cooked pasta and shredded gruyere cheese to the skillet with the cream sauce. Toss until well combined and the cheese is melted. If the sauce is too thick, add a splash of the reserved pasta water to reach your desired consistency.
8 oz Pasta, 1/4 cup Gruyère Cheese
Divide among bowls to serve. Top with the reserved crispy bacon. Serve with fresh parsley, additional gruyere cheese, and black pepper as desired.