Sift the cake flour into a bowl, then make a well in the center. Crack an egg in the center and whisk until it’s an even color and lightly frothy. Add the ice-cold beer to the egg and mix, slowly incorporating the surrounding flour until a smooth batter is created. Be careful not to over-mix the batter, which will form gluten and create a tougher finished product. Fill a second bowl (about the same size, if not slightly bigger) with crushed ice, enough water to create a small pool, and a tablespoon of salt. Place the first bowl over the second to keep the batter as cold as possible. Prepare the other ingredients and bring the fry oil to temperature while the batter rests for 30 minutes.