Preheat oven to 180ºC on a fan forced setting.
Place butter, zest and sugar into TM bowl and melt 3-4 min/37ºC/speed 2.
Add remaining crust ingredients and blend 15 sec/speed 6.
Press into springform cake tin with paper lined base. Reserve about 1 cup of the crust for the topping.
Bake for 18 minutes or until golden and fragrant. Cool.
Place all ingredients into TM bowl and blend 20 sec/speed 7. Scrape down if necessary and pour into base. Top with crumble mixture and steam in steam oven for 1 hour….OR, if you are being a Thermo mixer of extraordinary talent, place 1L water into Thermo bowl, place cheesecake on top of a pair of chopsticks (for easier steam circulation) and steam for 60 min/Varoma/speed 3.
Meanwhile, preheat oven to 180°C on a fan forced setting. Place steamed cheesecake into oven for 20 minutes until golden and a little crispy on top.
Roast a vanilla bean until crispy, about 10-15 minutes in 200ºC oven and then place in TM bowl with 140g good quality sugar of choice. Mill 10 sec/speed 10. Store in airtight jar until use.
Cool completely. Serve with dollops of whipped cream or mounds of the best vanilla bean ice cream available to you, which of course if you live in WA would be Azzura Gelati's award winning version and available at your local IGA store.