Youtu.be/VBxYhj97JV8

Steam the salted egg yolks for 10 minutes. Mash them into fine crumbs while still warm. Set aside.

Using a hand mixer, beat butter and sugar together for 2 minutes.

Sieve in flour, corn starch, and salt. Add the salted egg. Switch to a silicone spatula and mix until it becomes a homogeneous dough. If the dough feels sticky on your finger, wrap and refrigerate for 30 minutes until it is easier to handle. If not, continue to shaping.

Place the dough in between 2 sheets of parchment paper. Roll into a thickness of 1/4-inch (0.5cm).

Remove the upper sheet of paper. Cut-out as many pieces with a cookie cutter. Transfer them onto a tray lined with parchment paper. Gather the leftover dough and repeat the rolling process. If using a 1-1/4" (3cm) flower cookie cutter, you should be able to get at least 45 pieces.

To make the egg wash, whisk the egg yolk and water together. Brush it over the top of each cookie dough. Finally, top each with sesame seeds.

Bake in a preheated oven at 340°F (170°C) for 18-20 minutes or until golden brown. Let cool on a wire rack.