In a mixing bowl, toss your steak bites with Cajun seasoning, ensuring each piece is well-coated. Let the steak marinate for at least 10 minutes.

Boil a large pot of salted water over high heat, then add the medium pasta shells. Cook according to the package instructions until they are al dente, about 8-10 minutes. Once cooked, drain the shells in a colander and set them aside.

Heat a large skillet over medium-high heat and add a splash of cooking oil. Add the marinated steak bites in a single layer. Sear the steak for about 3-4 minutes, until they achieve a deep, caramelized color on one side before flipping. Cook for an additional 2-3 minutes until browned and just cooked through.

In the same skillet, reduce the heat to medium and add minced garlic. Sauté for about 30 seconds until fragrant, then slowly pour in the heavy cream, scraping the bottom of the skillet. Let the sauce simmer gently for about 2-3 minutes until it thickens slightly.

Reduce the heat to low and stir in the sharp cheddar and Parmesan cheeses. Keep stirring until the cheeses melt completely, creating a creamy sauce.

Return the seared steak bites and cooked pasta shells back into the skillet, tossing gently to coat everything in the sauce. Cook for an additional 1-2 minutes to heat through.