Originally from Family Style Food's "Mushroom Spinach Pasta with Shallots".
Optional:
Prepare/cook linguine in salted and slightly oiled water (you can save some pasta water, but I don’t end up using).
Heat oil in hot pan.
Add mushrooms and cook for a bit, add garlic (and shallots if using) and cook, add spinach and cook.
Then add linguine (add more oil if not enough for you and/or pasta water if you need it), salt to taste, red pepper flakes to taste. Add grated Parmesan cheese topping if you want.