In a glass bowl or large measuring cup, combine milk, 1/4 cup sugar, and yeast. Leave this mixture in a warm place for about 20 minutes. Once it becomes frothy, give it a quick stir.
Place the flour (start with 7 cups) and salt, and 3/4 cup sugar in the bowl of a stand mixer. Then pour the warm yeast mixture into the bowl.
Crack the eggs into a bowl and give them a quick whisk just to loosen them. Add the beaten eggs and vanilla extract to the rest of the ingredients in the mixer bowl.
Using the hook attachment, beat the dough until it begins to come together.
Cut the butter into slices and add 1/2 cup. Continue kneading the dough until the butter is well incorporated.
Add the remaining 1/2 cup slices butter and kneed the dough on high speed for about 10 minutes or until the dough is smooth and elastic. If the dough isn't coming together well enough, add the remaining 1/4 cup flour.
Place the dough onto a light floured surface and round it into a ball. Place it into a bowl greased with oil (lightly grease the top of the dough as well). Then cover with a cheesecloth and leave in a warm place for 1 hour or until it doubles in size.
Once the dough has proofed, divide it into 6 equal pieces. These six pieces will equal six small Nutella brioche loaves.
Form each piece into a ball, then roll it out to a circle 12 inches in diameter.
Evenly spread 1/4 cup warmed Nutella onto each dough circle. Then roll it up tightly. If you prefer more Nutella, you can add more. It just gets harder to work with when there is a lot of Nutella.
Using a sharp knife, cut the rolled up dough in half (lengthwise). Then cross over the 2 stands in a braid like fashion.
Spray 6 loaf pans with nonstick spray and place the braided Nutella brioche into the pans. Cover with a cheesecloth and let it proof in a warm place for 1 hour or until it doubles in size.
Once the dough has proofed, brush with egg wash (1 beaten egg + 1 tsp water) . Bake at 350 degrees Fahrenheit for 40 minutes until golden brown.