warm the milk to 110 degrees (even 30 seconds in the microwave sends it up to 130 for me, so make sure to let it cool a bit and use a thermometer so you don't burn your yeast in the following steps!)
add yeast and a pinch of sugar and set aside for 5 minutes, it should get foamy
using a dough hook, mix flour, sugar, salt, vanilla, zest, nutmag. add in the milk-yeast mixture and eggs
add half the butter and mix for 5 minutes
add the rest of the butter, mix for 5-7 minutes
the dough should pull away from the sides of the bowl and be able to hold a ball shape
slip the ball of dough in a greased bowl and let it rest in a warm place for 2 hours, covered with a towel
punch dough down and place in fridge for 24 hours
seperate the dough into 2 halves, roll each out to a 9x17'' rectangle and smear with any filling you choose
place each filled roll in the freezer for 10 minutes
take them out, slice them up the middle and wrap each slice around like a braid, when you reach the end fold the loaf in half and slip into a loaf pan that has been lined with a parchment paper hammock.
coat with streusel topping of your choice
let the loaves proof (if you don't have a proofing drawer, just slip the loaves in an oven with the light on and a pan of hot water on the rack below and the door closed) for about an hour and half
bake for 50 minutes at 350, the bottom should shound hollow when you take it out
immediately pierce with a poking thing and drizzle with simple syrup, pull out of parchment hammock and set on cooling rack