Mix the ingredients for the crumb topping together with your fingers and set it aside. With a rolling pin roll out half the challah dough to form a 16 x 12-inch rectangle. Using a spatula or the back of a spoon evenly spread the Nutella over the surface of the dough leaving a 1/4 inch border.

Sprinkle the surface with chocolate chips. Beginning with the widest side of the dough roll it up to form a roll and place this on a parchment-lined baking sheet. Place this inside the fridge or freezer to harden the dough slightly.

Remove it from the fridge and place it on a cutting board. Cut the log in half, using a very sharp knife. Pinch the top ends of both strands together. Twist the strands looping them over each other and pinch the bottom together.

Place this inside a greased or parchment-lined loaf pan. Sprinkle with the crumb topping over the top of the babka. Allow it to rise again for 30 minutes.

Preheat the oven to 350 F/175 C

Bake for 20-25 minutes until lightly browned on top.

MAKES 1