Pasta with Mushrooms and Spinach in Tomato Cream Sauce

box Barilla pasta (I used rigatoni)

extra virgin olive oil

small yellow onion (finely chopped)

container mushrooms (sliced)

garlic (minced)

fresh baby spinach (chopped)

can crushed tomatoes with basil

to 1/2 cup heavy cream

salt, crushed red pepper, parmesan cheese (to taste)

Sliced cooked chicken (optional)