Step 1

To make "water roux," whisk together water and flour in a small saucepan and cook, stirring, over medium heat until a very hot, gluey paste is formed. Mixture should reach at least 150 degrees F (65 degrees C). Remove from heat and let cool completely.

Step 2

While roux cools, pour 1/2 cup warm milk and yeast into the bowl of a stand mixer and let bloom for 10 minutes.

Step 3

Add the cooled starter, sugar, salt, beaten egg, flour, and butter to the yeast mixture. Using the dough hook, knead on low speed until a smooth, elastic, slightly sticky dough forms, about 10 minutes.

Step 4

Shape dough into a ball and transfer to a buttered bowl; let rise until doubled in size, 60 to 90 minutes.

Step 5

Transfer dough to work surface and press into a round disk. Use a bench scraper to cut dough like a pie, into 5 equal wedges. Form each portion into a ball of dough. Cover loosely with plastic wrap and let rest for 15 minutes.

Step 6

Generously butter a 10-inch springform pan, or 10-inch round cake pan. Cut a round piece of parchment paper to fit the bottom, place into the pan, and butter that as well. Set aside.

Step 7

Take one ball of dough and roll out on a lightly floured surface into an oblong shape, about 5 inches wide by 9 inches long. Take your bench scraper and make lots of lengthwise cuts, about 1/8 inch apart, starting 1/3 of the way from one of the ends, slicing all the way through the dough to the opposite end, forming many equal-sized strands of dough. When done, two-thirds of the dough will be sliced, and one-third will not be.

Step 8

Roll the unsliced part of the dough to flatten to 1/8-inch thickness. Place a rounded tablespoon of chocolate chunks (or the filling of your choice) in the center of the unsliced dough, and roll it up, tucking in the sides as you go, until the chocolate is covered, and you've reached the beginning of the cuts.

Step 9

Slowly roll up to form a "wool roll," being careful not to crush the sliced edges of the dough strands, finishing with the seam on the bottom. Transfer to the prepared pan, and place on the bottom, just barely touching the edge of the pan. Repeat four more times. Place the rolls around the inside of the pan to form a ring.

Step 10

Cover with plastic wrap and let dough double in size, 45 to 60 minutes.

Step 11

Meanwhile, preheat the oven to 350 degrees F (175 degrees C).

Step 12

Brush the bread's surface lightly with remaining milk.

Step 13

Bake in the center of the preheated oven until golden brown, 30 to 35 minutes. Let cool for 10 minutes. Remove from the pan and allow to cool completely on a wire rack before serving.