This is one of my all-time favorite kitchen tricks! The standard methods for testing for fish doneness are a) cutting into the fish to see if it’s opaque and b) using a fork to test if the fish flakes easily. However, there is a much simpler method! Test the internal temperature of the fish (this works with most fish) by inserting a small, sharp knife into the thickest part of the fillet. Hold it there for 10 seconds. Remove the knife, then carefully (sharp and hot!) lay the side of the knife against your upper lip or the inside of your wrist. Both areas are quite sensitive to temperature. If the knife is hot, the fish is done!