Photo by Martyn Thompson
YIELD: Makes about 32 hors d'oeuvres
ACTIVE TIME: 1 1D2 hr
TOTAL TIME: 1 1D2 Hr
Combine tortilla flour and water in a large bowl and knead with your hands until a uniform dough forms, about 1 minute. Pinch off enough dough to form a scant 3/4-inch ball. (Dough should be moist but not sticky when formed into a ball. If necessary, knead a little more tortilla flour or water into dough.) Form remaining dough into 3/4-inch balls, transferring to a plate, and cover with plastic wrap.
Very lightly oil comal (or pizza pan), then heat over medium-high heat until hot, about 2 minutes.
Press 1 ball of dough between plastic squares in tortilla press to form a 3-inch tortilla (about 1/16 inch thick). Peel off 1 plastic square, then, holding tortilla in your palm, carefully peel off other square and gently transfer tortilla to comal.
Cook until edges just loosen from comal and small brown spots appear on underside, 30 to 45 seconds. Turn over and cook, pressing flat with a metal spatula if necessary, until brown spots appear on underside, about 45 seconds. Turn over again and cook, pressing down with spatula, until tortilla inflates slightly (this may not always happen), 10 to 15 seconds. Enclose tortilla in folded cloth to keep warm and moist.
Make more tortillas, stacking them in cloth. (Once you get a rhythm going, cook more than 1 tortilla at a time.)
Cook garlic, chile, and 1/2 cup onion (reserve remainder for Garnish) in 2 tablespoons lard in a 10-inch heavy skillet over medium heat, stirring, until onion is softened, about 3 minutes. Add huitlacoche and 1/4 teaspoon salt and cook, stirring, until heated through, 3 to 5 minutes.
Assemble chalupas in batches just before serving:
Warm remaining 2 tablespoons lard (if using) to liquefy. Heat comal (or pizza pan) over medium heat until hot, then heat 8 mini tortillas, brushing tops lightly with some of lard (about 3/4 teaspoon each). While heating tortillas (1 to 2 minutes total), top each with about 1/2 teaspoon salsa, a sprinkling of reserved raw onion, and a rounded teaspoon huitlacoche mixture.
Transfer chalupas to a platter, then sprinkle with queso fresco and serve immediately.
Keep comal warm and repeat procedure when ready to serve next batch of chalupas.