Heat the milk until warm in a small saucepan or in the microwave for 30 seconds. The milk should not boil or get too hot, as this will kill the yeast. In a large bowl, or the bowl of your stand mixer, combine the yeast, 1 tbsp of the sugar and the warm milk. Cover for 10 minutes.
Once the yeast has bloomed, add in the rest of the sugar, the eggs and salt. Using the hook attachment on your stand mixer (or a wooden spoon), combine together until the butter starts to break up.
Gradually add the flour and continue mixing until a soft dough forms. It will feel slightly sticky to the touch. If it feels too sticky, add a couple tbsp of flour at a time until it reaches the desired consistency. If you are not using a stand mixer, knead the dough for about 5 mins on a floured surface.
Place the dough in a large, lightly oiled bowl, making sure the surface of the dough is also oiled. Cover the bowl with plastic wrap and let it sit in a warm space for about an hour - until the dough has doubled in volume.
In the meantime, grease 2 loaf pans and line with parchment paper.
Punch down the dough and divide equally into 2 portions. Roll one of the dough portions into a large rectangle. Spread evenly with half of the Nutella then roll into a log. Cut the log down the middle lengthwise, dividing the log into two long even halves. With the cut sides facing up, gently press together one end of each half, then lift the right half over the left half. Repeat until you get a long twisted plait. Repeat this process with the other dough portion.
Place each twisted babka plait into the prepared pan. Let them rise again in a warm space for another 40 minutes, or until the dough puffs up.
Preheat the oven to 180 C. Before baking, brush the dough with the milk and bake the babkas for 35-40 minutes, or until the tops are deep golden brown.
Once done baking, let them cool on a wire rack and then it is ready to serve.