Once your dough has doubled in size, turn the dough out onto a lightly floured surface. You will need to lightly flour the rolling pin too so the dough doesn't stick. Roll the dough into a rectangle that is ½ inch thick in height.
After the dough is rolled out, use a spatula to spread the chocolate filling evenly across the dough. Make sure to leave a ¼ inch border around the edges without filling.
Beginning with the longer side of the rectangle, tightly roll up the dough into a log. Lightly flour the dough as you go to help if it gets a bit sticky. Seal the roll by pinching the dough ends together. Then, flip the dough over so the pinched side is facing down.
Using a sharp knife, slice the log down the center. It's okay if this step gets messy, your babka will still turn out delicious! Then criss-cross the two halves of dough on top of each other with the filling facing up to form an X and twist the dough together.
Place the dough into the greased pan, adding back any loose filling and tucking ends under, if needed. Cover the dough with a towel or plastic wrap and let rest 45 minutes- 1 hour to proof a second time.