In a mixer bowl, soften the unsalted butter, then add in powdered sugar, and mix well.

Mix in egg yolk and vanilla extract, scraping the sides and bottom of the mixer bowl to combine well.

Sift in cake flour and salt, then use cut-and-fold method to mix until a dough forms.

Place the dough onto 2 large baking sheets. Use a rolling pin to roll out and flatten the dough into 3mm thickness.

Transfer the flattened dough to a freezer and chill for 30 minutes.

Preheat the oven to 170ºC.

Use cookie cutters to cut into your desired shapes, then transfer them to a baking tray lined with parchment paper. The dough will be hard after freezing, so be sure to press the cookie cutters firmly. This recipe makes about 18 individual cookies (i.e., 9 sand cookies).

Bake in the preheated oven for 10-12 minutes.

Allow the cookies to cool for a few minutes on the baking sheet before transferring them to a wire rack. Let cool completely.

In a pot, mix together heavy cream and earl grey tea powder.

Heat the mixture over medium heat until it just begins to simmer.

Remove from heat and pour it over chopped chocolates in a heatproof bowl. Let it sit for about 1 minute.

Stir gently until the chocolate is completely melted and the mixture is silky and smooth.

Transfer the earl grey chocolate ganache to a piping bag, pipe onto the bottom of each cookie, then place another cookie on top.