Bring a large pot of salted water to a boil. Add tortellini and cook until tender according to package instructions. Stir occasionally, then drain and set aside. Reserve a small amount of pasta water.

Heat olive oil in a large skillet over medium heat. Add diced chicken in a single layer. Season with salt, pepper, and Italian seasoning. Cook without stirring for a few minutes, then flip and continue cooking until chicken is fully cooked and lightly golden.

Add minced garlic to the pan. Stir continuously and cook for about one minute until fragrant. Do not let it brown.

Pour in chicken broth and stir, scraping up any bits from the bottom of the pan. Slowly add heavy cream and mix well. Let the sauce simmer gently over medium-low heat until slightly thickened.

Stir in pesto until fully combined and the sauce turns evenly green. Add Parmesan cheese and stir until melted and smooth.

Add cooked tortellini into the sauce. Gently mix to coat evenly. Add cherry tomatoes and spinach. Stir slowly and allow spinach to wilt.

If the sauce is too thick, add a small amount of reserved pasta water and stir until desired consistency is reached.

Remove from heat and let rest for 2 to 3 minutes before serving. Serve warm.