1 green chile or jalapeño pepper, seeded and minced
1/3 cup thinly sliced scallions
1 lime, juiced and zested
1 tbsp unseasoned rice vinegar
2 tbsp chopped fresh cilantro
2 tbsp chopped fresh mint
Prepare slaw: In a medium bowl, add all slaw ingredients. Toss to combine and set aside in refrigerator, covered, until ready to serve.
Preheat grill to medium. Place a large sheet of aluminum foil on a baking sheet and lightly mist it with cooking spray.
In a plastic bag with a zip-top closure, combine coriander and cumin seeds. Gently crush seeds with a rolling pin or flat side of a meat tenderizer. Empty crushed seeds onto a large plate.
Rinse mahi mahi and pat dry with paper towels. Gently press both sides into seed mixture and place fish on foil-lined baking sheet. Transfer baking sheet to grill, cover and cook for 10 minutes, or until fish is just opaque at the centre and flakes easily with a fork. Remove from grill and carefully wrap edges of foil around fish to keep warm (use oven mitts or tongs for assistance).
Warm tortillas on grill for 1 to 2 minutes per side.
To assemble tacos, slice fish into 1- to 2-inch pieces. Divide evenly among tortillas and top each with about 1/2 cup slaw.