Light your campfire, grill, or stovetop grill. While your grate warms up, prep your ingredients. Soak your dried corn husks in boiling water, cover with a wet towel or heavy plate to fully submerge them for at least 30 minutes. While the corn husks rehydrate, combine lime zest, shallot, and 2 tablespoons of the chopped cilantro with the softened butter, using a fork to mix.
Then, cut your fish into equal pieces, pat dry and season with salt and pepper to your liking.
Once your husks have been rehydrated, create a fan shape using one large or two medium husks (one stacked halfway over the other) ensuring there are no slits in the shape. With another corn husk, pull apart 8 portions to create about ½ inch thick stands to use as string. Place one piece of fish in the middle of the “fan” along with 1½ tablespoons of the butter mixture and wrap, as if folding a paper in 3. Using your husk string, tie both ends, double knotting to let as little amount of butter and steam escape. Repeat with the remaining pieces of fish. If using shrimp, simply divide into 4 equal portions.
When the heat of your grate is at a high temperature, cook your corn until kernels turn golden and charred. Remove from the grill, cut kernels off the cob, and toss in a large bowl with remaining cilantro, onion, tomato, and lime juice. Add salt to taste. Then, add your husk wrapped fish over the heat and grill for about 15 to 20 minutes, flipping halfway through. Remove from heat. Carefully remove husk sting and unfold the husk to expose the fish, being careful not to spill the butter. Top with a generous scoop of corn salsa and serve immediately.