1. Preheat oven to 400ºF. Line a baking sheet with parchment. Place cornstarch and salt into a large ziplock bag. Place coconut and panko into second ziplock bag, breaking up any clumps of coconut. Shake bags to mix contents. Whisk egg whites in a shallow bowl until foamy.
2. Place shrimp into ziplock bag with cornstarch mixture and shake until shrimp are coated evenly. Dip shrimp, a few at a time, in egg whites. Shake off excess and drop shrimp into ziplock bag with coconut mixture. Shake until shrimp are coated. Place in a single layer on baking sheet and bake, turning once, until coconut is golden and shrimp are cooked through, 15 to 20 minutes. Serve immediately.