Bring a large pot of salted water to a boil and cook the penne pasta according to package directions until al dente.
While the pasta cooks, toss the steak strips with Cajun seasoning, garlic powder, smoked paprika, salt, and pepper in a bowl.
Heat the olive oil in a large skillet over medium-high heat and sear the steak strips until browned and cooked to desired doneness, then remove from the pan and set aside.
In the same skillet, melt the butter and sauté the minced garlic until fragrant.
Reduce heat to medium and pour in the heavy cream and whole milk, scraping up any browned bits from the bottom of the pan.
Whisk in the cream cheese until smooth, then stir in the mozzarella and Parmesan until the sauce is melted and creamy.
Add the cooked pasta and seared steak back into the skillet with the sauce.
Toss everything together until well coated and heated through.