Spaghetti with Creamy Mushroom, Beef, & Balsamic Sauce

 dry spaghetti

  tablespoons  extra virgin olive oil

yellow onion; diced

  pound  button mushrooms (, thinly sliced)

  cloves garlic (, finely chopped)

  pound  ground beef

 14.5- ounce can diced tomatoes (, undrained)

  cup  heavy cream

. dried marjoram

 fresh flat-leaf parsley leaves (, roughly chopped)

. balsamic vinaigrette

Parmesan cheese for garnish