Mildly spicy dried chiles, such as ancho or New Mexico, add moderate heat and rich flavor to dishes. Look for whole dried chiles in the produce section of large supermarkets and New Mexico or ancho chili powder in the spice section of large supermarkets or online.
Mahi-mahi (also called dorado) from the U.S. Atlantic and halibut from the Pacific are both sustainably fished.
Two ways to warm corn tortillas: (1) Microwave: Wrap stacks of up to 12 tortillas in barely damp paper towels; microwave on High for 30 to 45 seconds. Wrap tortillas in a clean towel to keep warm. (2) Oven: Wrap stacks of 6 tortillas in foil; place in a 375°F oven for 10 to 15 minutes. Wrap tortillas in a clean towel to keep warm.
To oil grill grates, dip a folded paper towel in cooking oil, hold it with tongs and rub it over the grates. Do not use cooking spray on a hot grill.
To make ahead
Prepare coleslaw (Step 2) up to 4 hours ahead.