01 - Bring a large pot of salted water to a rolling boil. Cook the cheese tortellini according to package directions until al dente. Drain thoroughly and set aside.
02 - Season the diced chicken breasts evenly with salt, pepper, and Italian seasoning. Heat olive oil in a large skillet over medium-high heat. Add the seasoned chicken in a single layer and cook until golden brown and cooked through, approximately 5 to 7 minutes. Remove the chicken from the skillet and set aside on a plate.
03 - In the same skillet, melt the butter over medium heat. Add the chopped onion and sauté for 2 to 3 minutes until softened and translucent. Add the minced garlic and cook for an additional minute until fragrant, stirring constantly to prevent burning.
04 - Pour the chicken broth into the skillet and deglaze, scraping up all the flavorful browned bits from the bottom of the pan. Reduce the heat to medium and stir in the heavy cream and grated Parmesan cheese. Continue stirring until the cheese has fully melted and the sauce begins to thicken slightly, about 3 minutes.
05 - Add the fresh baby spinach to the skillet and gently stir until wilted and incorporated into the sauce, approximately 1 to 2 minutes.
06 - Return the seared chicken to the skillet along with the cooked tortellini. Gently toss everything together until evenly coated in the creamy garlic sauce. Taste and adjust seasoning with additional salt and pepper as needed. Serve immediately, garnished with extra Parmesan cheese and chopped fresh parsley if desired.