Optional: Combine ingredients for the diy cajun seasoning blend. This will make about
Cook pasta to al dente according to package directions. Drain and set aside on a plate or in a large bowl until ready to use.
Meanwhile in a large, deep skillet, heat 1 tablespoon olive oil and 1 tablespoon butter. Add chicken and season with 2 tablespoons Cajun seasoning and 1/2 teaspoon kosher salt. Cook until chicken is no longer pink; about 5 minutes. Transfer to a plate and set aside with the pasta.
Add 3 tablespoons of butter to the skillet and melt, swirling around to coat. Stir in garlic and cook for about 30 seconds to a minute.
Whisk in about 1/4 cup of the chicken broth and stir constantly to deglaze (loosen and scrape up all those lovely brown bits of flavor) the pan if needed, then stir in flour and cook for about one minute or until golden.
Whisk in milk and remaining chicken broth and simmer for several minutes until thickened (sauce should coat the back of a spoon).
Remove from heat and stir in Parmesan cheese until melted. Add Parmesan in small handfuls to avoid clumping, stirring each time until completely melted.
Toss the cooked pasta and chicken with the sauce to coat.
Serve immediately, garnished with diced tomatoes and fresh chopped parsley.
Notes
Adjust the spice level by either making your own Cajun seasoning blend with the linked recipe, or using less of your chosen blend.