Once the dough has doubled in size, turn out onto a lightly floured surface.
Using a rolling pin, roll out into a long thin rectangle. The dough should be between ⅛ and ¼" thick
Spread the cooled chocolate ganache on top of the dough.
Sprinkle the milk and semisweet chips in an even layer on top of the ganache.
From the long side of the rectangle, starting in the middle and working your way out bit by bit, roll up the dough tightly. You may need to lift up and stretch the dough as you roll to ensure that the dough rolls tightly
Once the dough is rolled up, cut the log in half to make two loaves. Next, cutdown the center of the log to reveal the layers.
Twist the two halves together and lay into a parchment lined loaf tin. Repeat with the other half of the dough.
Leave the loaves to proof until puffy, around 1.5 hours.
Preheat the oven to 350 degree Fahrenheit when it looks like the loaves are looking about ready
Bake for 40-50 minutes or until very golden brown. If the loaf is getting too dark, cover with aluminum foil to prevent burning.
While the loaves are baking, make the syrup. Combine the sugar and water in a sauce pan and bring to a boil, stirring occasionally to ensure the sugar dissolves. Once the mixture is boiling, reduce heat and simmer for 5 minutes to allow some of the water to boil off and create a thick syrup. Remove from heat and let cool.
Remove the babka from the oven when done brush generously with the syrup. Leave in the tin to cool.