Note These bite-sized tacos work a treat at parties. The guacamole can be made ahead, but be sure to cover it closely to prevent oxidation and browning. 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.