- Combine grouper with vinegar and lemon juice in shallow bowl. Cover, refrigerate, and allow acids to “cook” grouper for about 30 minutes.
- While grouper is in refrigerator, poach shrimp by bringing all poaching liquid ingredients to simmer in stockpot. Add shrimp, and simmer, uncovered, until pink and tails curl (2 to 5 minutes, depending on size of shrimp). Cool immediately.
- Chop cooled poached shrimp. Add to large mixing bowl. Mix in grouper, all remaining ceviche ingredients, and serve immediately with Cumin Crackers.
For Cumin Crackers:
- Preheat oven to 350 degrees and lightly grease 2 cookie sheets.
- In medium bowl, whisk together all dry ingredients until combined.
- With pastry cutter or two forks, cut butter into dry ingredients until mixture resembles coarse meal. Stir in milk, just to combine.
- Knead cracker dough until tacky and smooth. Divide into 2 round balls and let rest 10 minutes.
- On lightly floured surface, roll each dough ball to about ⅛-inch thickness. Place on greased sheet pan, prick all over with fork, lightly sprinkle salt, and bake for about 10 minutes—rotating after 5 minutes—until evenly golden brown. Cool and break into rustic triangles.