01 - Bring a large pot of generously salted water to a rolling boil. Add the cheese tortellini and cook according to package directions until they float and are tender. Drain through a colander and set aside.
02 - While the pasta cooks, heat olive oil and butter together in a large skillet over medium-high heat. Season the chicken pieces with salt, pepper, and dried Italian herbs. Add the chicken to the hot skillet in a single layer and cook for 6 to 8 minutes, turning occasionally, until golden brown and cooked through to an internal temperature of 165°F. Transfer the chicken to a plate and tent loosely with foil.
03 - Reduce the heat to medium. In the same skillet with the rendered drippings, add the chopped onion and sauté for about 3 minutes until softened and translucent. Add the minced garlic and stir constantly for 30 seconds until fragrant, taking care not to let it brown.
04 - Pour in the heavy cream and add the cream cheese and grated Parmesan. Stir continuously and let the sauce simmer gently for 2 to 3 minutes until all the cheese has melted and the sauce is smooth and velvety.
05 - Add the chopped fresh spinach to the skillet and fold it into the sauce. Cook for 1 to 2 minutes, stirring occasionally, until the spinach is just wilted and bright green.
06 - Return the seared chicken and cooked tortellini to the skillet. Gently toss everything together until the pasta and chicken are evenly coated in the creamy garlic sauce. Taste and adjust seasoning with additional salt and pepper as needed.
07 - Serve immediately in warmed bowls. Garnish with extra grated Parmesan and a sprinkle of chopped fresh parsley if desired.