Make the levain as instructed in the recipe. Make sure it is active and bubbly before proceeding.
Place active levain, eggs, butter, milk and sugar into the Thermomix bowl and blend 6 sec/speed 6..
Add remaining dough ingredients and mix 10 sec/speed 6.
Knead 3 min/Interval. Knead by hand into a tight ball and place in a buttered bowl, covered until doubled in size. This may take up to 4 hours or longer.
Roll dough into large rectangle and cover with a clean cloth while you make the filling.
To make filling, place cinnamon stick, vanilla bean and sugar into TM bowl and mill 20 sec/speed 10. Add butter and blend 6 sec/speed 6.
Use a floured bread mat to do some pull and folds on the dough. Then roll the dough out to as large a rectangle as you can without pulling on the dough. It should be fully centred on the bread mat and the same shape.
Dot the surface of the dough with filling and spread carefully so as not to tear the dough. Roll up, into a long sausage shape and cut lengthwise through the entire roll, so that you can see the filling. Stick the ends together and wind the two pieces of dough, cut side out around each other. Transfer to a loaf tin quickly, pushing at either end to fit. Cover and rise again while you pre-heat the oven to 200°C.
Reduce the temperature to 180°C and bake for 40 minutes until golden and fragrant.
Whilst still hot brush liberally with maple syrup.
Allow to cool in the tin slightly before removing. Slice and serve with butter or eat the next day toasted...so good!