Preheat the oven to 150℃/300℉. Line a cookie sheet with baking paper. Draw 2-inch(5cm) circles on the paper with 1-inch distance between them.

Into a large bowl, add butter and powdered sugar. Beat with a whisk/electric beater/stand mixer on medium speed till creamy and smooth.

Add egg and vanilla essence. Mix till well combined.

Add salted caramel and mix till well combined.

Sift in all-purpose flour and cornflour. Mix till well combined.

Fill the dough in a piping bag fitted with a star-tipped (or any of your preference) nozzle.

Pipe the dough in the drawn circles on baking paper.

Bake in the preheated oven for 15-18 minutes or until the cookies turn golden colour. Let the cookies cool down on the baking sheet itself.

Remove from hot water and set aside till it reaches room temperature.

Add chilled milk and beat on high to medium speed till a creamy smooth consistency is achieved.

Fill the caramel ganache into a piping bag.

Place the cookies bottom side up. Pipe chocolate ganache on 12 cookies. Cover with the remaining 12 cookies to make sandwich cookies.

Place the cookies in an airtight container or cover them with a plastic wrap and place it in the fridge for at least 30 minutes or until ready to serve.