Cook pasta as directed on the package, then set aside. While pasta is cooking, start next steps.
Wipe your mushrooms off with a damp towel or quickly rinse and dry well. Slice them into thick slices – mushrooms shrink a ton when cooked and thicker slices cook the best.
In a large saute pan, add your oil and butter and turn the heat up to medium high. Once hot, add mushrooms and make sure you allow some space between the mushrooms. Cook for 4-5 minutes before touching them. Then give them a good stir so that the other side cooks and gets nice and brown.
Turn the heat down to medium and add garlic and 1/3 of the broth to deglaze the pan. Cook for another minute.
Add milk and salt; stir to combine. Add the cooked pasta and the remaining broth.
If you are adding spinach, cut using a chiffonade method. To do this, stack the spinach leaves on top of each other and roll them into a ‘burrito’. Using a sharp knife, make very small cuts creating strips. Add to pan.
Stir in Parmesan and cream cheese; cook another 2-3 minutes or until heated through and the cheese is melted. Serve warm and enjoy!