Sift flour, baking powder, and salt into a medium bowl. Add brown sugar. Whisk eggs, milk, and vanilla in another bowl. Whisk in flour mixture until smooth.Advertisement
Heat oil in a large saucepan until a deep-fry thermometer registers 375 degrees. Place batter in a pastry bag fitted with a 1/4-inch round tip. Holding a wok sieve just below oil's surface, pipe batter into oil over sieve, swirling it onto itself to create a 3-inch rosette shape. Fry, turning once, until golden on both sides. Drain on a paper-towel-lined plate. Repeat with remaining batter. Just before serving, dust with confectioners' sugar.