Drain 3 tablespoons of oil from the sun-dried tomato jar into a large skillet or pot with sides. Chop the sun-dried tomatoes and set aside.
Heat the skillet over medium-high heat. Add the cubed chicken, 3 teaspoons Italian seasoning, paprika, red pepper flakes, salt, and black pepper. Cook until the chicken is golden brown and fully cooked, about 5 minutes.
Stir in 1/4 cup parmesan cheese and cook for another minute. Remove the chicken from the skillet and set aside.
In the same skillet, melt the butter. Add the shallot, garlic, and remaining Italian seasoning. Cook until fragrant, about 3 minutes.
Pour in 3 1/2 cups water and bring to a boil. Add the pasta and cook, stirring frequently, until al dente, about 8 minutes.
Stir in the heavy cream, Dijon mustard, remaining parmesan cheese, spinach, and chopped sun-dried tomatoes.
Return the cooked chicken and any juices to the skillet. Stir until the spinach wilts and the sauce becomes creamy.
Finish the Creamy Sun-Dried Tomato Chicken Pasta with fresh lemon juice and extra parmesan cheese before serving.