Start cooking about 30m before serving.
Eat right away after being cooked. As soon as they start to cool down, they are not so good anymore.
2 servings
Knead the masa harina with salt and water.
Grate the mozzarella.
Spread cling film on the work surface and spread a little oil with the fingers on top of the cling film.
Split the dough in 4, leaving a little extra for patching the pupusas while shaping them. Form a ball from each piece of dough.
Oil the palms of your hands and then, taking one dough ball at the time, form a disc in your palm. Cup the hand and add a mound of cheese on the disc. Bring the edges of the disc together to form a ball filled with cheese. Carefully flatten the balls in 6in discs, patching the holes with some of the remaining dough. Place the discs back on the oiled cling film.
Once all pupusas are formed, heat a non-stick or cast iron pan with just a little oil. When it’s hot, place as many pupusas in as would fit. Fry on a side until golden with browned spots then turn and fry the other side the same way. This could be 2-4 min depending on how hot the pan is. Expect some cheese to start oozing out.
Serve right away with curtido or an avocado salad. Don’t wait to finish frying all of them, but eat them as soon as they are made.