Place the chicken breasts in a gallon zipper bag with 1 tablespoon olive oil and 1 tablespoon Cajun seasoning; seal and shake or knead to coat evenly.
Heat the remaining 1 tablespoon olive oil in a large skillet over medium-high heat.
Add the chicken breasts to the hot pan, cover, and cook about 7 minutes; flip and cook another 7 minutes, or until chicken reaches 165°F (times may vary with thickness).
While the chicken cooks, start the pasta in a pot of boiling salted water and cook according to package directions; drain when done.
In a medium heavy saucepan over medium heat, melt the butter. Whisk in the flour until combined to form a roux.
Add the cream cheese and minced garlic to the roux and whisk until incorporated; it may be slightly lumpy at first.
Pour in 1/4 of the half and half and whisk until smooth, then stir in the grated Parmesan.
Slowly whisk in the remaining half and half and bring the sauce to a gentle boil, whisking frequently until it thickens. Season with salt, pepper, and additional Cajun seasoning to taste.
Pour the sauce over the drained pasta and stir to combine.
Slice the cooked chicken and either stir into the pasta or arrange on top, then serve immediately.
