01 -
Preheat oven to 175°C and line a baking tray with baking paper.
02 -
In a mixing bowl, beat the softened butter and icing sugar until the mixture becomes light and creamy.
03 -
Add egg white and vanilla extract, then continue beating until the mixture is smooth.
04 -
Gradually sift in flour, cornstarch, and salt. Mix gently until just combined, forming a thick dough.
05 -
Transfer the dough into a piping bag with the tip cut off. Pipe the dough into square, thin shapes onto the prepared tray.
06 -
Use a scraper or offset spatula to level the surface of each square for even thickness.
07 -
Bake for 13-15 minutes, or until the edges are lightly golden brown. Monitor closely to prevent overbaking.
08 -
Transfer cookies to a wire rack and allow them to cool completely.
09 -
Melt the white chocolate gently over a water bath or in the microwave at low power, stirring until smooth.
10 -
Spread or pipe a thin layer of melted white chocolate onto the base of one cooled cookie, then sandwich with another cookie. Repeat with remaining pieces. Let set until the chocolate is firm.