Beat the eggs, sugar, and salt together until well blended.

Add the flour, milk, and vanilla, and beat until the batter is completely smooth. The batter should be thin, almost like crepe batter.

Pour the vegetable or canola oil into a deep, heavy pot until it is about 2 1/2 inches deep. Heat the oil to 365-375°F.

Set the rosette iron in the hot oil for about 2 minutes to warm it up.

Lift the iron out of the oil, let the excess drip off, and then dip it into the batter up to 1/4 inch below the top.

Lower the iron into the hot oil and fry until the cookie is golden, usually taking 10-30 seconds.

If the rosette does not slip off by itself, use a fork to nudge it loose. Flip it briefly if necessary to brown the other side.

Drain the cookie on a paper-towel-lined rack. Ensure to lift the iron out and tip it upside down to remove extra oil.

Reheat the iron in the oil for about 1 minute before making the next rosette. Stir the batter occasionally as oil can get into it.

Dust the cookies with confectioners' sugar once they are cool, waiting to dust if storing for a few days.