No need to preheat the oven yet, this dough needs to chill.

Place flours, salt, bicarbonate of soda and Revels into a medium sized bowl and stir until all of the chocolate is coated in flour. Leave to one side.

Place butter and sugars into a large bowl, or the bowl of your stand mixer and beat until light and fluffy, about 2 minutes on medium-high speed.

Scraping sides as necessary, add in the eggs and vanilla and beat on med-high speed until well incorporated, about 1 minute.

Tip in the flour mixture and mix on low until a soft dough forms.

Tip your dough into the bowl you measured flour in and cover with cling film. Place in the fridge for at least 6 hours, overnight if possible.

Once chilled, preheat the oven to 180C/350F and line 2-3 baking trays with grease proof paper/silicone mat/Silpat etc.

Cut each of the fun size Mars Bars in half.

Using a 1.5tbsp cookie scoop, make 2 dough balls and flatten each slightly. Place half of a Mars Bar onto one of the flattened dough balls, then take the other disc of dough and place on top of the Mars Bar.

Pick up your cookie stack and push together slightly, then press and pull the edges on the bottom and top of each disc until they meet and form one big dough ball.

Repeat with all of the cookie dough, I made 13 cookies. Each one has 3tbsp of cookie dough, so I would advise only putting 6 cookies on each baking tray and leaving plenty of space between them, because these are BIG cookies!

Place in the oven for 12-14 minutes, until golden around the edges and slightly under baked and soft in the centre.

Leave to cool on the baking trays for 15 minutes, before transferring to a wire rack to cool completely.

Once cool, place slightly cooled melted Galaxy chocolate into a small piping bag fitted with a size 1 or 2 writing tip. On every Revel that you see on the top of a cookie, pipe 8 legs around it to create a spider. Most of my cookies had two visible Revels, so two spiders.

Leave for 20-30 minutes for the chocolate to set and then devour! You can also heat the cookies for 10-20 seconds in the microwave to make the Mars Bar centre gooey again.

Cookies will keep in an airtight container, at room temperature for 5 days.