Cube the 225g butter up before softening, and then soften it!
In a large bowl, cream together the cubed and softened butter with the caster sugar and salt until it gets light and fluffy!
Beat in the eggs with a fork until it gets fully incorporated!
In a separate bowl, sieve together the flour, cocoa powder and baking soda!
Add the dry ingredients to the large bowl, and mix them all together until they are well combined and make a dough!
Turn the dough out onto a surface and push it together and into a flat square! Wrap it in cling film and put it in the fridge to rest for one hour!
Go do something else for a bit!
Once the dough is close to finishing it's resting, preheat your oven to 160C/fan 140C/gas 3!
Take out the dough from the fridge and divide it into 4 pieces before placing a piece between two sheets of parchment/baking paper! (This is done instead of flouring a surface as the flour gets into the dough and affects the colour!)
Roll the dough out between the two sheets of paper until it is at 1/2cm thickness! If the dough is being tough to roll, press it down with your hands first!
Use a small round cookie cutter (or your closest analogue!) to cut the dough into individual cookies! Place on a tray lined with baking/parchment paper! Make sure to leave some space between each cookie! At least a centimetre!
Reroll any uncuttable parts of the dough into a ball and roll out until you've got all the cookies you can out of the piece of dough!
Repeat the last 3 steps with each piece of the dough until you've used as much of it as you can! You should get roughly 40 individual cookies! Also I'd place the remaining dough on the baking sheet in whatever shape you like to have as an extra little treat!
Bake in the oven for 15 minutes! If you're using multiple trays, rotate them around halfway through the cooking time!
While the cookies are baking, make the filling!
Combine the 115g of butter with the icing sugar and vanilla extract in a small bowl and beat together until it is light and fluffy!
To assemble the cookies, take one cookie (use the flatter side!) and spread on a generous amount of the filling with a knife or spoon! Then take another cookie (flatter side again!) and sandwich it together with the other cookie! Give it a light squeeze to squeeze out any excess filling! Don't worry if you run out of filling as you can always easily make more!
And you're done! The cookies can be eaten straight away but I recommend leaving them to rest in the fridge for a bit so they get nice and cool and so that the filling sets!
