Beat together the butter, sugar and tahini until light and fluffy (about 3-5 min). I use my KitchenAid with the paddle attachment but you can also use hand beaters or the Thermomix.
Add the egg/egg yolk and vanilla paste and keep beating for about 3 more minutes.
Mix the dry ingredients in a bowl and then add to the mixer. Mix until just combined (don't over mix).
Add the chocolate chips and fold in. The mixture should be quite wet, rather than dry.
Put the mixture in the fridge for 12 hours/ overnight.
Preheat your oven to 170 degrees Celsius and line a baking tray.
Roll a tablespoon of mixture (not too big though as these spread) per cookie. Leave a decent amount of space between each cookie though.
Place a chocolate melt on top of each ball and push it down slightly. then put the cookies in the oven for 12-15 minutes for soft cookies. If you want crunchy ones give them another 2 or 3 minutes.
Once the cookies are done, melt a handful of the chocolate melts and put in the piping bag. Snip a very small part of the tip on and pipe 4 legs on each side of the chocolate melt on the top of the cookie to create legs. then pipe two dots on the chocolate melt and add the eyes.
Sprinkle salt flakes over the top and serve