Whisk the cream of mushroom, milk, mascarpone (or cream cheese), sour cream and half of the shredded cheese in a large bowl. Add the ground beef mixture, rice, and fold together to combine. Pour into the greased baking dish and top with remaining cheese.
Bake, covered with foil, for 20 minutes. Remove the foil and broil until the top is caramelized and crispy. Sprinkle with Italian parsley and serve immediately.
Recipe by Slice of Jess at https://sliceofjess.com/cheesy-hamburger-and-rice-casserole/