Prepare the Ingredients: Slice the mushrooms evenly, dice the onion, and cut the bacon into small cubes for quick, even cooking. Finely mince the garlic so it blends smoothly into the sauce later. Chop the fresh parsley for a bright finish.
Cook the Bacon: Heat a large pan over medium heat with just a drizzle of oil. Add the cubed bacon and cook, stirring occasionally, until it starts to crisp and release its fat — about 4–5 minutes. The bacon should be lightly golden and aromatic but not overly crunchy.
Sauté the Onion and Garlic: Add the diced onion directly into the pan with the bacon. Sauté for 2–3 minutes until the onion softens and turns translucent, picking up flavor from the rendered bacon fat. Stir in the minced garlic and cook for another 30 seconds until fragrant. Avoid browning the garlic, as it can become bitter.
Cook the Mushrooms: Add the sliced mushrooms to the pan. Stir to coat them in the flavorful bacon and onion mixture. Let them cook undisturbed for a couple of minutes before stirring again — this helps them brown nicely. Continue cooking for about 5–7 minutes, until the mushrooms are tender and lightly caramelized. Season with salt and black pepper to bring out their earthy flavor.
Build the Sauce: Pour in the chicken broth to deglaze the pan, scraping up any browned bits from the bottom with a spatula. These bits add a deep, savory flavor to the sauce. Stir in the heavy cream and bring the mixture to a gentle simmer. Let it cook uncovered for about 10 minutes, stirring occasionally, until the sauce reduces slightly and thickens enough to coat the back of a spoon.
Finish the Sauce: Taste the sauce and adjust seasoning with more salt and pepper if needed. Stir in a handful of fresh chopped parsley for color and freshness.
Combine and Serve: Toss the hot, cooked spaghetti directly into the pan or pour the sauce generously over individual portions. The sauce should cling to the pasta beautifully. Garnish with extra parsley or a sprinkle of grated Parmesan cheese if desired, and serve immediately.
