Pour milk into a bowl and activate the yeast per the package instructions (if using instant yeast, skip activation).
Add flour, eggs, sugar, vanilla, salt, and half the butter. Mix for 3-4 minutes.
Gradually add the remaining butter and continue mixing/kneading for another 4 minutes until combined.
Shape the dough into a flattened square, wrap it in plastic, and refrigerate for 8-12 hours.
Remove dough from the fridge, flour your workspace, and roll it into a 10x28-inch rectangle.
Spread Nutella evenly (important!) over the dough, then sprinkle with chocolate chips.
Roll the dough into a 28-inch log, then cut into three 9-inch pieces.
Slice each piece in half lengthwise to create six strips.
Form an "X" with each pair of strips, then twist them together to form three twists.
Place each twist into an 8x3 inch loaf pan, tuck the ends under, cover, and let rise in a warm spot for 60 minutes.
Preheat oven to 350°F. Bake for 25-30 minutes until the internal temperature reaches 180°F.
Immediately brush the tops with the cooled syrup.
Allow loaves to cool completely for 2 hours before slicing to ensure they are fully set. This is important!