Line a rimmed baking sheet or flat plate with parchment paper. Melt the butter and let it cool until it is just barely warm.
Place the dough on a work surface and let it sit for about 10 minutes. Flour the work surface and roll it out to a 14 x 5-inch rectangle. Brush the dough with the melted butter.
Spread 4-5 tablespoons of the chocolate filling on the dough and leave about a 1/4-inch border all the way around. Lightly press the chocolate filling into the dough.
Starting at the long edge roll the dough into a tight spiral. When it’s rolled up, place the seam-side down and press it into the surface. Trim the edges so the log is 12-inches long. Cut the log into 8 pieces, 1-1/2 inches long each.
Place the unbaked rugelach on a tray and refrigerate them for at least one hour.
Repeat the above steps for the other 3 pieces of dough.
At this point, the rugelach can also be frozen and baked directly from the freezer. Place the rugelach in a single layer on a baking sheet or board, Freeze them, then place them in a freezer bag. When ready to bake, remove them from the freezer, brush them with the egg wash, sprinkle with the sugar and bake until golden brown.