1. Whisk together eggs, granulated sugar, milk, and vanilla in a large bowl, then add flour and salt, whisking, until just combined (do not overmix, or cookies will blister).
2. Heat oil in a 3- to 4-quart heavy saucepan with rosette iron in it until thermometer registers 370 to 375 degrees F. Carefully lift out iron, letting oil drip off into pan. Dip all but top edge of iron into batter 3 seconds, then submerge iron in oil and fry (batter adhering to iron) until golden, 35 to 40 seconds (do not let go of iron; cookie will shatter if it hits bottom of saucepan). Lift out iron, letting oil drip off, and, working over paper towels, carefully pry off rosette with a fork. Let rosette drain, hollow side down, on paper towels, then make more rosettes in same manner, heating iron in oil 10 seconds before dipping it into batter each time.
3. Dust rosettes with confectioners sugar before serving.

Yield: 30 servings