Cook spaghetti in salted water until al dente. Reserve ½ cup of pasta water before draining.
In a large skillet, cook bacon over medium heat until crispy. Remove and set aside, leaving a little bacon fat.
Add olive oil and butter to the same pan. Toss in mushrooms and sauté until golden brown.
Add garlic and cook for 30 seconds until fragrant. Don’t walk away — garlic burns fast.
Return bacon to the pan. Add drained spaghetti and a splash of pasta water to loosen things up.
Toss everything together. Season with salt and pepper.
Garnish with parsley and serve with grated parmesan if you’re feeling extra cheesy.