Place sugar into the Thermomix bowl and mill 40 sec/speed 10.
Add milk, salt, maple syrup and butter and cook 10 min/70°C/speed 3.
Add chocolate and cook 15 min/100°C/speed 3.
Remove MC and cook 35 min/Varoma/speed 2 using simmering basket on the lid to prevent spattering and help with reduction.
Add vanilla bean paste and blend 4 min/speed 7 with basket in place on lid. Scrape into a buttered 18cm square tin and allow to cool completely before refrigerating for up to 2 hours prior to cutting and serving.