Cook tortellini according to package directions.
Drain in colander.
Meanwhile, in a large skillet, sauté the mushrooms, garlic and onion in ¼ cup butter until tender.
Remove and keep warm.
In another sauce pan, combine milk (or cream) and remaining butter.
Bring to a gentle boil over low heat; stir in cream cheese cubes with whisk.
Add salt, pepper, oregano, basil, Italian seasoning, thyme, parsley and red pepper flakes.
Cook and stir at low heat until smooth and sauce thickens.
In a large bowl, mix tortellini, well-drained spinach, mushroom mixture and sauce.
Spread into a greased 10x15” baking dish.
Top with Italian cheese blend and bake at 350˚, covered with foil, until heated through and cheese melts, perhaps 45 minutes.
Add an extra half cup or cup of cheese and heat an additional 5-10 minutes until cheese melts.