Drain about 3 tablespoons of oil from the jar of sun-dried tomatoes into a large skillet or Dutch oven. Finely chop the tomatoes and set them aside.

Heat the reserved oil over medium-high heat. Add the cubed chicken, 3 teaspoons Italian seasoning, paprika, red pepper flakes, salt, and black pepper. Cook for about 5 minutes until the chicken is lightly browned.

Sprinkle in ¼ cup Parmesan cheese and continue cooking for another minute. Remove the chicken from the skillet and set aside.

Melt the butter in the same skillet. Add the chopped shallot, garlic, and the remaining Italian seasoning. Cook for about 3 minutes until fragrant.

Pour in 3½ cups of water and bring to a boil.

Stir in the pasta and cook, stirring often, until al dente, about 8 minutes.

Reduce the heat to low. Stir in the heavy cream, Dijon mustard, remaining Parmesan cheese, chopped sun-dried tomatoes, and baby spinach.

Return the cooked chicken and any accumulated juices to the skillet. Stir until everything is coated in the creamy sauce and the spinach has wilted.

Squeeze fresh lemon juice over the pasta, stir gently, and serve immediately with extra Parmesan cheese.