Cook the tortellini according to package instructions in a large pot of salted boiling water. Drain and set aside.
In a large skillet over medium heat, melt 2 tablespoons of butter. Add the diced chicken and season with salt, pepper, and Italian seasoning. Cook until the chicken is golden brown and cooked through, about 6-8 minutes. Remove the chicken from the skillet and set aside.
In the same skillet, add the remaining 2 tablespoons of butter and minced garlic. Sauté for about 1 minute until fragrant.
Pour in the heavy cream and bring to a gentle simmer. Stir in the grated Parmesan cheese, mixing until the cheese has melted and the sauce is smooth.
Add the cooked tortellini, sautéed chicken, and fresh spinach to the skillet. Toss gently to combine and heat through, about 2-3 minutes. Adjust seasoning with salt and pepper as needed.
Serve immediately, garnished with chopped fresh parsley.