Place the butter in a large saucepan and melt over low heat.

Use your hands to tear the filo pastry into small pieces and place in the saucepan.

With the heat on medium, use a spatula or wooden spoon to move the filo around until crunchy, golden and toasted. This can take at least 5 minutes. Remove from the heat and tip into a bowl.

Remove the lid from the jar of pistachio cream and microwave for 10-20 seconds. Give it a stir until it's melted and smooth.

Pour the pistachio cream on top of the toasted filo (save 2 tablespoons for the decoration) and stir until fully coated. Set aside and leave to cool.

Chop the butter into chunks and place in a large mixing bowl. Beat with an electric mixer or wooden spoon for a few minutes, until it's soft and broken up but not at the 'creamed' stage.

Mix in the light brown sugar and white caster sugar until the mixture is combined and looks like wet sand. Try not to over-mix at this stage otherwise the butter will become too soft.

Mix in both of the eggs. The mixture won't look very appealing at this stage but don't worry it will do soon!

In a separate bowl, whisk the self-raising flour, plain flour, cocoa powder and salt together until combined. Add to the butter mixture and fold to make a thick cookie dough.

Fold in the chocolate chips.

Line a baking tray or tin (one that will fit inside your freezer) with greaseproof paper.

Break off large heaped tablespoons of cookie dough and flatten in the palm of your hand. Add a teaspoon of the pistachio filling in the middle and wrap the dough around it to make a ball. Repeat until all the dough is used up, you should be able to make 12 cookies in total.

Place the rolled cookies on the baking tin and wrap the tin tightly in foil. Freeze for 90 minutes.

Towards the end of the freezing time, preheat the oven to 200°C fan / 220°C conventional. Line a large baking tray with greaseproof paper and place the tray in the oven for 5 minutes to heat up. The heated tray will give the cookies a crisp outside but gooey middle.

Place 4-5 frozen cookies on the preheated tray, leaving space between each.

Bake for 12-15 minutes until firm on the edge but soft in the middle. The cookies should still be thick with little spread. You can use a round cookie cutter to scoot them into shape.

Leave the cookies to cool on the baking tray for 15 minutes.

Remove the lid from the jar of pistachio cream and microwave for 10-20 seconds. Give it a stir until it's melted and smooth.

Pipe or drizzle the melted pistachio onto of the cookies. Then tuck in and enjoy!