• Add the warm milk, yeast, and sugar to the bowl of a stand mixer fitted with a dough hook attachment. If using active dry yeast, let this mixture sit for 5-10 minutes until foamy. 
• Add the flour, eggs, vanilla, and salt to this milk mixture. Mix on slow speed until a thick dough forms.
• Next, add in the room temperature butter, a few cubes at a time, and keep mixing to incorporate the butter.
• Turn the mixer to medium speed and keep mixing until the sticky dough strengthens and passes the windowpane test. It should pull away cleanly from the sides of the bowl.
• Shape the dough into a ball on a lightly floured work surface, then place it into a lightly oiled bowl. Cover the bowl with a lid or plastic wrap and let it proof in a warm place until doubled in size. 

Filling and shaping

• Mix softened butter, cookie butter, brown sugar, and cinnamon in a medium bowl with an electric mixer into a creamy paste.
• Grease and line two 9x5 inch loaf pans with parchment paper.
• Deflate the dough and pull it from the bowl onto a lightly floured surface. Weigh the dough on kitchen scales and cut it into two equal pieces.
• Take one piece and use a rolling pin to roll it into a rectangle measuring around 11x14 inches (27x35 cm rectangle).
• Dollop half the cookie butter mixture over the rectangle in little pieces. Use an offset spatula to spread it out, leaving a ½ inch (1cm) border around all the sides.
• Roll it up, from the long edge of the dough into a log, jelly roll style. Place it in the fridge for 15-20 minutes to chill. Repeat with the other dough piece and the remaining filling. 
• Once chilled, slice a log in half lengthwise with a sharp knife to expose the filling. Take the top two ends and fold them over. Lift the left half over the right half, then the right over the left, and repeat down, exposing the cut sides and buttery layers of biscoff spread filling. When you reach the end, tuck the dough underneath to compact the loaf.
• Place the braid into a prepared loaf pan. Repeat the process with the second half of the dough. On top of the twisted loaf, press pieces of broken biscoff biscuits.
• Loosely cover and let the babkas undergo a second rise until they nearly double in size, around 1-2 hours. The rising time depends on room temperature.

Baking

• Preheat the oven to 350°F/180°C and place a rack in the middle. Bake the risen babkas for approximately 35-40 minutes until deep golden brown. If they are browning too much, loosely cover the tops with foil. 
• While baking the babkas, prepare the sugar syrup to glaze them. Combine the sugar and water in a small saucepan over medium heat. Bring it to a simmer until the sugar dissolves, then remove it from the heat. 
• Once the babkas are removed from the oven, brush the top of the babka liberally with the syrup. I avoid getting too much on the pieces of cookie pressed on top so they stay crispy.
• Let them cool in their pans for 20 minutes, then remove them and let them cool further on a wire rack.