In a medium bowl, beat the two eggs. Add the cold sourdough discard and mix. Add enough ice cold water to reach a pancake batter consistency (see note above about this). Set aside. Lightly season the fish with salt and pepper, then lightly coat with flour. For the onion petals, remove them from the water and lightly coat with flour. In a appropriate pan, heat ½ inch of oil to 350-375 degrees. I use a large cast iron pan for this job, which is perfect. When your oil is hot, dip your lightly floured cod into the tempura batter, then transfer the fish to the hot oil. Do not crowd the pan; leave space between pieces of fish. Cook the fish for about 3 minutes, then flip it over and cook the other side for another 3 minutes. Transfer fish to a wire rack to drain any excess grease. For the Vidalia onion petals, cook them the same as the fish (they take a little less time). Use your eyes to help decide when things are done; we are going for a crispy golden brown crust. Eat! Serve your fish and “chips” with a lemon slice or malt vinegar. We went ahead and whipped up a quick tarter sauce as a condiment for our meal.
