Preheat your oven to 350 degrees Fahrenheit and spray a 12-inch oven-safe skillet with non-stick spray.
Cut the pepper jack cheese, cream cheese, and queso blanco into chunks and place them into your oven-safe skillet.
Mix in the minced garlic, thawed spinach, drained Rotel, and diced green chiles into the skillet with your cheeses. Sprinkle the cajun seasoning and pour in one cup of evaporated milk.
Bake for about 20 minutes or until everything can be easily stirred together into a creamy dip consistency.
Add in sour cream, parmesan cheese, and any remaining evaporated milk until you achieve your desired consistency. Spread out your dip evenly in the skillet before topping it with shredded cheese.
Return the skillet to the oven for another 15 minutes or until the dip is gooey and bubbly on top. Optionally, switch your oven to broil for 1-2 minutes for a golden brown finish.