Mix the masa harina with 1 teaspoon of the salt, then work in the warm water until you have a soft dough that holds together without cracking when you press it flat between your palms.

Let the dough rest 10 minutes, covered with a damp cloth, so the flour hydrates fully. Add water a tablespoon at a time if it still feels dry.

Divide into 8 balls and press each into a disc about 3.5 inches wide and a quarter inch thick, using a tortilla press lined with plastic or the flat bottom of a dish.

Cook the discs on a dry comal or heavy skillet over medium heat, 2 minutes a side, until the surface looks matt and set but has taken no colour.

Take one off the heat and, while it is still too hot to hold comfortably, pinch a rim around the edge with your fingertips, protecting them with a cloth. The masa is pliable now and will crack once it cools.

Repeat with the rest. Warm the mashed beans in a pan with the remaining salt and a splash of water until spreadable.

Heat the oil in a skillet over medium-high and fry the sopes base down, 1 to 2 minutes, until the bottom is golden and firm. Do not submerge the rim.

{'Drain on a rack, then fill': 'beans first, then lettuce, salsa, sour cream and queso fresco. Serve at once.'}