Rosa Martha Toledo and Julio Bustillos serve these delicious little half-moons as a cocktail party appetizer at their garden restaurant, Bar Jardín in Juchitán. Odilia Román, the chef, shared her recipe with me. You can vary the amount of chiles to taste—this amount makes a fairly spicy filling.
If you are not a sardine lover, use two 6-ounce cans tuna packed in oil instead.