Cook tortellini according to package directions. Reserve 1 cup of the pasta water for later, then drain the pasta and set aside.
Meanwhile, cube the chicken into 1 inch pieces, dice the onion, slice the mushroom, halve the tomatoes, mice the garlic, and chop the basil.
Heat 2 Tbsp. of olive oil in a large skillet and pan sear the chicken. Salt and pepper them while they cook. Once the chicken obtains a golden color, remove and set aside in a bowl.
In the same skillet, add the remaining 2 Tbsp of olive oil and bring to heat. Add the onions and allow them to caramelize just a bit.
Add the mushrooms and garlic. Mix them together and cook until tender.
Add the half and half, cream cheese, pasta water, black pepper, salt, pesto, and tomato halves. Mix and cover to cook on low for 2-3 minutes.
Next, add in the chicken, parmesan cheese, and spinach. Mix and cover to cook again for a couple more minutes.
Finally, add in the cooked tortellini and mix everything together to coat the tortellini with the sauce. Cook for 1-2 minutes and then remove to serve.
Garnish with some basil leaves or parmesan cheese.