First, add the yeast, sugar, and milk to the mixing bowl and warm for 3 min. / 37°C / Speed 2.
Next, add the remaining dough ingredients—the flour, butter, and pinch of salt—and knead for 5 min. / Dough mode until a smooth dough forms.
Turn off your Thermomix® and let the yeast dough rise right in the covered mixing bowl for 30 minutes.
After the first rise, knead the dough once more for 30 sec. / Dough mode.
Then, let it rise in the mixing bowl for another 30 minutes.
In the meantime, melt the butter for the filling in the microwave or in a small saucepan, then stir in the sugar and cinnamon. Set aside to cool slightly so the mixture thickens up a bit.
After the second rise, preheat your oven to 175° C convection.
Transfer the dough from the mixing bowl onto a lightly floured work surface, and
use a rolling pin to roll it out thin into a rectangle (about 50 x 30 cm).
Spread the cinnamon-sugar butter mixture evenly over the dough, reserving a small amount for later. An offset spatula or cake server works amazingly well for spreading it evenly! Be sure to spread the filling all the way to the edges so they don't dry out.
Next, roll the dough up tightly starting from the long edge to form one long log.
Using a sharp knife, slice the log into pieces about 3–4 cm thick.
To get that classic Franzbrötchen shape, press the handle of a wooden spoon down right through the center of each slice, causing the filling to bulge out at the sides (see photo).
Transfer the pastries to a baking sheet lined with parchment paper and bake for about 15 minutes. Keep an eye on them toward the end, as every oven bakes a little differently!
While still warm, brush them with the reserved butter-sugar-cinnamon mixture, then cover with a clean kitchen towel and let them cool down.