This was a failure for me, but I'd love to get the recipe right because my friend from Guatemala describes pupusas as delicious cheese-filled delights. (OK, those are her exact words, but you get the point.) Mine turned out thick and chewy and tasted raw.
2 cups masa harina
1 cup warm water
1 cup queso fresco, in small pieces
In large bowl, mix together masa harina and water. Knead in more water, one Tbsp. at a time if needed, to make a moist yet firm dough. (It should not crack on the edges when you push down on it.) Cover, and set aside 5 to 10 minutes.
Roll the dough into a log, and cut it into 8 equal pieces. Roll each piece into a ball. Either use a tortilla press or two pieces of wax paper to roll each piece of dough into a 5- to 6-inch circle. Divide filling evenly among four pieces of dough, and cover with remaining dough and seal edges with fingers.
Heat an ungreased skillet over medium-high heat. Cook each pupusa about 1-2 minutes per side, until lightly browned and blistered. Serve warm.