Cook the pasta according to the package instructions until al-dente stage.
Drain and keep it aside.
In a large pan, heat the butter until it melts on low heat.
Sauté onion into the butter and cook it until soft or pink in color.
Stir in garlic and cook it for two more minutes.
Add milk to the pan and bring it to a boil.
Add cream cheese, spinach, salt, and black pepper powder to the milk.
Let all of it cook for 2 to 3 minutes and then add the cooked pasta to the pan.
Add cheddar and parmesan cheese to the pasta and cook it all for 2 to 3 minutes or until you get a gooey consistency of the sauce. Add ½ a cup of water to the pan if the sauce turns too thick.
Serve hot pasta and garnish it with parsley!