Season the cubed chicken with 1 teaspoon of Italian seasoning, salt, paprika, red pepper flakes, and black pepper.
In a large skillet, melt 2 tablespoons of butter over medium heat. Add the seasoned chicken and cook until golden brown and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set it aside.
In the same skillet, add the diced onion and cook for about 3-4 minutes until translucent. Then, add the minced garlic and cook for an additional 1 minute until fragrant.
Add the sundried tomatoes (including some of the oil) to the skillet with the onions and garlic. Stir to combine and let the flavors meld for about 2 minutes.
In a separate pot, bring 2 cups of water to a boil. Add the uncooked pasta and cook according to package instructions until al dente. Drain and set aside.
Pour in the heavy whipping cream into the skillet with the sautéed vegetables and sundried tomatoes. Stir well and let it simmer for 2-3 minutes until the sauce thickens slightly.
Return the cooked chicken to the skillet, along with the drained pasta and fresh spinach leaves. Toss everything together until well coated in the creamy sauce.
Stir in the grated Parmesan cheese until melted and combined. Taste and adjust the seasoning if necessary.
Serve hot, garnished with the shredded Parmesan cheese and fresh spinach leaves if desired.