1) In a medium-sized mixing bowl, blend together the eggs, sugar, milk and vanilla.
2) Sift together the salt and flour. This will lighten up your batter and help to keep it smooth. Add the flour to the egg mixture and whisk until no lumps remain. If you have a few, small stubborn lumps, you can pour the mixture through a strainer.
3) Refrigerate the batter,covered, for at least 30 minutes, but no longer than 60 minutes.
4) When you are ready to fry, heat 4 inches of good quality cooking oil in a deep pan to 365°F. Arrange a layer of paper towels on a baking sheet and top with a wire rack. This will be your draining tray.
5) Dip your rosette iron into the hot oil for one minute. Remove the iron from the oil, blot lightly on paper towels, then dip into the rosette batter. The batter should come about 3/4 of the way up the iron, but should not go over the top of the iron design.
6) Hold the iron in the batter for a few seconds, then lift to drain off excess batter. Submerge the iron back in the hot oil to fry the rosette. After about one minute, the rosette should drop off of the iron into the oil.
7) While the rosette finishes frying, you can re-dip the iron into the oil, then the batter to start a second rosette frying. As the first rosette becomes golden, flip it with a pair of tongs to brown the other side.
8) Drain the rosettes on the wire rack, hollow side down to eliminate excess oil. Serve warm with powdered sugar or cinnamon sugar.
9) Yield will vary by the size of your iron. Rosettes can be stored loosely covered for 2 to 3 days, or frozen in a single layer for up to 3 months.