Fill the piping bag. Gently, without pressing the batter. If you're using a zip-top bag, cut about 2 cm (¾ in) off one corner now.
Pipe the strips. With the bag at 45° and 1 cm (⅜ in) above the paper, strips 2 x 10 cm (¾ x 4 in), 2 to 3 cm (1 in) apart. Don't linger: the batter is losing air.
Dust with powdered sugar. Optional. A single light layer, sifted from 20 to 30 cm (8 to 12 in) high, and straight into the oven: with no baking powder, the only air is in the egg whites, and it escapes while the batter sits.
Bake for 15 minutes. Tray on the middle rack or one lower, and don't open the oven for the first 10 minutes. They're done when they're pale golden and the surface is dry and firm.
Dry them for 15 more minutes. At the same temperature, with a sheet of aluminum foil on the top rack or with bottom heat only, so they don't brown too much.
Peel them off. With a silicone mat: slide it off the hot tray onto the counter and leave it for 5 minutes. Then lift one end of the mat and slowly bend it downward: the ladyfingers release on their own. With parchment paper: let them cool on the tray for 15 to 20 minutes. Then bring the paper to the edge of the table and, instead of lifting the ladyfingers, pull the paper downward so it's the paper that comes away from them.
Move them to a wire rack. Leave them until they're completely cool. Air circulates underneath, so the steam they still release doesn't soften the bottoms.
Store them airtight. In an airtight container or a zip-top bag, at room temperature.