In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and cream cheese. Add the 2 tablespoons granulated sugar, vanilla and salt and beat at medium speed until mixture is light and fluffy. Reduce speed to low, and slowly beat in the flour until dough starts to pull away cleanly from the sides of the bowl. Be careful not to overmix. Tip dough out onto a floured work surface and divide into two halves. Shape each half into a disk, wrap in plastic wrap and refrigerate for at least 1 hour.
To make the filling, mix the hazelnuts (or walnuts), brown sugar, remaining granulated sugar, cinnamon and a pinch of salt in a food processor and pulse until finely ground.
Preheat the oven to 350°F. Line two baking sheets with parchment paper. On a lightly floured surface, roll out one dough disk into a 9-inch round, less than 1/8 inch thick. Spread Nutella evenly in a thin layer over the surface, leaving a 1/4" border around the outside. Sprinkle half the nut and sugar mixture on top and gently press into the nutella and dough.
Cut the round into 12 equal-sized wedges, like a pizza. (In fact, a pizza cutter is ideal for this.) Starting on the outside edge at the wide end of each triangle, roll up each slice to form little crescents. Pinch to seal the end and place on the prepared baking sheet, point side down. When all 12 crescents are rolled, refrigerate and repeat the process with the rest of the dough.
Brush the tops with the egg wash. Sprinkle with sugar and bake until golden brown, 25 to 30 minutes.