Warm milk in microwave for 40 - 50 seconds on HIGH. It should be warm, but not hot.
Combine milk, sugar, and yeast and let sit for 5 minutes or until foamy.
Place flour and salt in the bowl of a stand mixer fitted with a dough hook. On low, add yeast mixture and cooled butter. Combine until smooth. Increase speed and knead for 3-5 minutes.
Place dough in a large bowl that has been "greased" with oil, turning to coat the dough.
Place in a warm place and allow to rise until doubled in size, about an hour. Divide dough in half and work one half at a time.
Roll each half into a rectangle on a lightly-floured surface.
Spread Nutella down the middle third of the rectangle lengthwise.
With a sharp knife, cut 1-inch strips down both sides of dough from filling to edge.
Starting at one end, fold a strip from one sides towards the middle. Next, fold the strip directly across over onto the first strip. Repeat. (See How to Braid Bread for further directions.)
Place on a baking sheet and let rise for about 1 hour or until it has doubled again. (I like to spray my loaves with nonstick spray.)
Bake loaves for 20 to 25 minutes in an oven that has been preheated to 350 degrees.
Remove from the oven and allow to cool before cutting. Store in an airtight container.