Pipe 6 blobs of pistachio spread onto a baking sheet lined with parchment paper and freeze for at least 1 hour.

In a large mixing bowl, cream together the melted butter, caster sugar, and light brown sugar until smooth.

Add the egg yolks and milk to the butter and sugar mixture, and mix until well combined.

In a separate bowl, sift together the plain flour, dark chocolate powder, baking powder, and bicarbonate soda.

Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms.

Fold in the chopped white chocolate and milk chocolate until evenly distributed throughout the dough.

Using a cookie scoop, scoop out a portion of dough and flatten it slightly.

Place one of the frozen pistachio blobs in the center of the dough, then wrap the dough around the pistachio, ensuring it is completely covered.

Repeat this process for the remaining dough and pistachio spread.

Place the filled cookie dough balls back in the freezer for 2 hours to firm up.

Preheat your oven to 180°C (350°F) during the last 10 minutes of freezing.

Once the cookies are hard to touch, place them on a baking sheet lined with parchment paper, leaving some space between each cookie.

Bake the cookies in the preheated oven for 12-15 minutes, or until the edges are set and slightly golden.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.