Preheat oven to 170ºC and line the base of a 23cm spring form cake tin and set aside.
To make chocolate batter place sugar into Thermomix bowl and mill 10 sec/speed 10.
Add butter and vanilla and chop 6 sec/speed 6.
Add cocoa, eggs and yoghurt and blend 6 sec/speed 6. Scrape down sides of bowl.
Add flour and baking soda and powder. Just combine 12 sec/Interval. Turn into prepared tin and place tin into fridge.
To make pistachio batter, place pistachios, tonka bean and sugar into a clean Thermomix bowl and blend 20 sec/speed 8. Scrape down sides of bowl and repeat, adding the almond oil through hole in lid to create a paste.
Add eggs, butter and cream and blend 6 sec/speed 6. Scrape down sides of bowl and repeat.
Add remaining dry ingredients and just combine 12 sec/Interval.
Place handful chocolate chips on top of chocolate batter. Pour pistachio batter on top carefully spreading so as not to dislodge the chocolate batter.
Bake 60 minutes or until inserted skewer comes out clean.
Cool on wire rack before removing from tin.
To make ganache, place chocolate into the Thermomix bowl and chop 6 sec/speed 10. Add cream and cook 5 min/60ºC/speed 2. Cool slightly before pouring over cold cake.
Garnish with additional choc chips, pistachios as desired.