In Mexico, queso fresco, fresh cheese, is commonly crumbled over dishes like this. It's difficult to find in Australia, but feta makes a good substitute.
Note White masa flour (also known as masa harina or harina de maíz) is a white nixtamalised corn flour. If you don't have a tortilla press, you can use a rolling pin to flatten the tortillas. White masa flour and tortilla presses are available from Mexican food shops including Monterey Mexican Foods.