Preheat oven to 170°C. Line a slice tray with baking paper.
Place all base ingredients (except butter and vanilla) into the Thermomix bowl. Combine 6 sec/speed 5.
Add butter and vanilla. combine 10 sec/speed 5.
Place half of the crumb mixture into the tray. Bake for 15 minutes. Cool slightly. Increase oven temp to 180°C.
To make the filling, insert Butterfly and place all ingredients into the Thermomix bowl. Combine 20 sec/Butterfly/speed 3. Scrape down sides of bowl and repeat.
Pour the filling over the base then top with remaining crumb. Bake for 20-25 minutes, until golden and fragrant.
Refrigerate for at least 2 hours before slicing. It is quite a crumble, as the title suggests!
This freezes very well and only needs to be at room temperature around 15 minutes before being completely serve-able.