Add bacon to a large skillet then place over medium heat and let bacon slowly render its fat and brown. Once browned, scoop bacon onto a paper towel lined plate to drain. Remove all but 2 Tablespoons bacon grease from the skillet.

Meanwhile, turn heat under skillet up to medium-high then add mushrooms and shallot and stir to coat in bacon grease. Let mushrooms sit and sear until they release their liquid, 2-3 minutes, then saute, stirring occasionally, until the liquid has cooked off. Add garlic and dried thyme then continue sauting until the mushrooms are golden brown and tender, 5 minutes, turning heat down slightly if needed to prevent garlic from burning.

Add heavy whipping cream and chicken stock then turn heat up slightly to bring to a simmer. Add parmesan cheese then stir until smooth. Add baby spinach then stir and simmer until spinach is barely wilted, 1 minute.

Use tongs to transfer pasta directly from the cooking pot to the skillet (or if you had to drain it, add pasta from colander). Stir gently and constantly with tongs, adding 1/4 cup pasta cooking water at a time to create a smooth and creamy sauce - just keep stirring! When the pasta is tender and the thickened sauce clings to the pasta, it's done.

Turn off heat then add a drizzle of fresh lemon juice (dish shouldn’t taste lemony - just brightened) the cooked bacon, lots of freshly cracked black pepper, and salt to taste. Scoop into bowls then garnish with more parmesan cheese, if desired, and serve.