Prepare the base way in advance. Up to 2 weeks if you keep them in the fridge out of sight! They will need less baking time than the original cookies, as they are probably smaller, unless you are going for a bigger tart.
Prepare any fillings other than ganache in advance so they are cold and spoonable.
To make the ganache, place all ingredients into the Thermomix bowl and melt 5 min/50°C/speed 1 or longer if not fluid enough to pour out of the bowl easily. Scrape down sides of bowl as needed to ensure all the chocolate melts.
Pour into the prepared tartlet cases.
If you are using other fillings, knock yourself out, but the chocolate one is a bit yummy. It reminds me of Kingston biscuits!