1. Adjust oven racks to upper-and lower-middle positions and heat oven to 225°F. Line 2 baking sheets with parchment paper. Combine sugar, cornstarch, and espresso powder in small bowl.

2. In standing mixer fitted with whisk attachment, beat egg whites, vanilla, and salt at high speed until very soft peaks start to form (peaks should slowly lose their shape when whisk is removed), 30 to 45 seconds. With mixer running at medium speed, slowly add sugar mixture in steady stream down side of mixer bowl (process should take about 30 seconds). Stop mixer and scrape down bottom and sides of bowl with rubber spatula. Return mixer to high speed and beat until glossy, stiff peaks have formed, 30 to 45 seconds.

3. Working quickly, place meringue in pastry bag fitted with 1/2-inch plain tip or large zipper-lock bag with 1/2 inch of corner cut off. Pipe meringues into 1 1/4-inch-wide mounds, about 1-inch-high, on baking sheets, 6 rows of 4 meringues on each sheet. Bake 1 hour, rotating pans front to back and top to bottom halfway through baking. Turn off oven and allow meringues to cool in oven at least 1 hour. Remove from oven and let cool to room temperature before serving, about 10 minutes.

Makes 48 small cookies