In a food processor, combine the flour, sugar, baking powder, and salt. Add the butter and pulse until the mixture has the texture of sand. Add the egg and vanilla. Pulse again until the dough just begins to form. Shape into a disc with your hands and cover with plastic wrap. Refrigerate for 30 minutes.
With the rack in the middle position, preheat the oven to 180 °C (350 °F). Line a baking sheet with parchment paper.
On a floured work surface, roll out the dough to about 3-mm (1/8-inch) thick. Cut 30 cookies using a 4 ½-cm (1 ¾-inch) round cookie cutter. Place the cookies on the baking sheet.
Bake for about 10 minutes or until lightly browned. Let cool.
In a small saucepan, sprinkle the gelatin over the water and let bloom for 5 minutes.
Add the sugar. Melt over low heat, stirring until the sugar and gelatin have dissolved.
Pour into a bowl. Add the corn syrup and vanilla and beat with an electric mixer until soft peaks form, about 10 minutes.
With a pastry bag fitted with a 2-cm (3/4-inch) plain in diameter and filled with meringue, top each cookie with a dome of meringue. Let cool for 30 minutes at room temperature.
In a bowl, over a double boiler or in the microwave oven, melt 140 g (5 oz) of chocolate. Remove from the double boiler and add the remaining chocolate. Stir until the chocolate is smooth. If necessary, put back over the double boiler for a few seconds if the chocolate does not melt completely. Be careful not to overheat the chocolate, it might bloom when cooled.
Dip the cooled cookies, marshmallow side down, in the chocolate, flip and remove from the chocolate with a fork. Shake to remove any excess chocolate.
Place the cookies on a lightly oiled wire rack or a baking sheet lined with parchment paper. Refrigerate for about 30 minutes. Serve at room temperature.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.