Making the Pistachio Filling

1. Melt 1 teaspoon of unsalted butter in a large saucepan over low heat.
2. Tear the filo pastry sheets into small pieces and add them to the pan.
3. Stir the pastry continuously over medium heat until golden and crispy, about 5 minutes. Remove from the heat and transfer to a bowl.
4. Microwave the pistachio cream for 10-20 seconds to soften it, then stir until smooth.
5. Pour the melted pistachio cream over the toasted filo pastry, saving 2 tablespoons for decoration. Mix until fully combined, then set aside to cool.

Preparing the Cookie Dough

1. Chop the butter into small pieces and place it in a large mixing bowl. Beat with an electric mixer or a wooden spoon for a few minutes until soft but not fully creamed.
2. Add both sugars and mix until the texture resembles wet sand. Avoid over-mixing to prevent the butter from becoming too soft.
3. Add the eggs one at a time, mixing until incorporated. The mixture may appear uneven at this stage, but it will come together once the dry ingredients are added.
4. In a separate bowl, whisk together the self-raising flour, plain flour, cocoa powder, and salt.
5. Gradually add the dry ingredients to the wet mixture, folding gently to form a thick cookie dough.
6. Fold in the chocolate chips until evenly distributed.

Filling and Shaping the Cookies

1. Line a baking tray or a tin (one that fits inside your freezer) with greaseproof paper.
2. Take a heaped tablespoon of cookie dough and flatten it in your palm.
3. Place a teaspoon of the pistachio filling in the center and wrap the dough around it to form a ball.
4. Repeat until all the dough is used, making approximately 12 cookies.
5. Arrange the rolled cookies on the baking tray, cover tightly with foil, and freeze for 90 minutes.

Baking the Cookies

1. Preheat the oven to 200°C (fan) or 220°C (conventional).
2. Line a large baking tray with greaseproof paper and place it in the oven for 5 minutes to heat up. This ensures crisp edges while maintaining a soft center.
3. Place 4-5 frozen cookies on the preheated tray, leaving space between each.
4. Bake for 12-15 minutes, or until the edges are firm but the centers remain slightly soft.
5. If needed, use a round cookie cutter to gently shape the cookies while they are still warm.
6. Allow the cookies to cool on the baking tray for at least 15 minutes before decorating.

Decorating the Cookies

1. Microwave the reserved pistachio cream for 10-20 seconds until smooth.
2. Pipe or drizzle the melted pistachio cream over the cookies before serving.