If queso ranchero is unavailable, use Monterey jack, sharp Cheddar or chevre. Epazote has a pungent flavor and its strength can vary depending on when in the season it was harvested. It's less pungent when the plant is young, so start with a few bits of leaf and add more depending on your taste.
Queso ranchero or other soft white cheese
Flour or corn tortillas
Fresh epazote leaves
Grease lightly and heat a nonstick skillet or griddle over medium heat. Cut cheese into slices about 1/8-inch thick. Place cheese slices on flour or corn tortilla. Cut epazote leaves finely and sprinkle over cheese. Place another tortilla on top of the cheese and epazote leaves. Place on the nonstick skillet or hot griddle and toast gently, turning frequently so the tortilla does not burn. The quesadilla is done when the tortilla is "freckled" and the cheese is starting to melt.