Corn flour

Corn flour is not the same as cornmeal, cornstarch, polenta, or masa harina. In the U.S., look for Bob’s Red Mill brand, or others such as My Spice Sage online. If you can’t find it, grind cornmeal in a high-powered blender or dedicated spice grinder for several minutes, until finely ground, then strain through a mesh sieve (you may regrind the larger particles if you like, or add them back to your bag of cornmeal).