Cook the tortelloni in a large saucepan according to the packet instructions. Drain well and set aside.
Heat the broth in a saucepan. Cut the onions into small cubes, slice the mushrooms, and roughly chop the ham.
Heat oil in a large saucepan over medium heat. Add the onions and cook for 2 minutes, stirring occasionally. Add the ham and cook for 1 minute. Add the mushrooms and cook for 2 minutes. Pour in the broth and cream, then immediately stir in the cream cheese. Bring to a boil, then remove from heat. Season with salt and pepper to taste.
In a small bowl, mix the flour with 1-2 tablespoons of water until smooth. Stir this into the sauce. Return the saucepan to medium heat and bring to a boil for 1 minute, stirring constantly.
Place the tortelloni in a large baking dish and pour the sauce evenly over them. Sprinkle the grated cheese on top. Bake at 180°C (350°F) on the middle rack for 25 minutes until golden brown.