With the rack in the middle position, preheat the oven to 190 °C (375 °F). Line a baking sheet with a Silpat mat or a sheet of non-stick aluminum foil. Do not use parchment paper, the result is not satisfactory.
In a bowl, combine the flour and cornstarch.
In another bowl, beat the egg whites and sugar with an electric mixer for 30 seconds.
At low speed, add the dry ingredients alternately with the oil, water and vanilla.
On the prepared baking sheet, spread 15 ml (1 tablespoon) of batter per cookie in a 10-cm (4-inch) disc. Prepare 3 to 4 cookies per sheet. Bake for 8 to 10 minutes until 1-cm (1/2-inch) of the cookie is golden brown all around.
Warning, this next step must be done quickly. Place a strip of paper in the centre of each cookie. With a small metal spatula or a butter knife, fold the cookie in half-moon. Fold down the straight side of the cookie on the edge of a glass. Let cool.
To avoid burning your fingertips, it is best to put white cotton gloves when handling hot cookies.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.