Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper.
In a large bowl, whisk the flour, sugar, cocoa powder, baking powder and salt until combined. Add the butter. You can do this by shredding it in with a grater or cutting it into small chunks and working with a pastry cutter or your fingers.
In a separate bowl, whisk together the egg and cream. Slowly pour the wet ingredients into the dry ingredients and stir until the dough just comes together. Gently and briefly knead the dough with your hands – be careful not to overwork the dough. Gently knead in the hazelnuts. The dough will be very dry. If you need to add a little more cream, go ahead.
Empty the dough onto your work surface and mash it down. If flour is not completely absorbed, use a spatula or a bench scraper to scrape up dough and flatten it again until flour is worked in. Shape dough into a rectangle approximately 4 by 10 inches and spread about 2 tablespoons of the Nutella over it. Roll the dough up to make a cylinder, turn it on its end, and gently flatten it into a disk (circle) about 1 3/4 inches high. Slice the circle int 4 triangles.
Place your Nutella Scones dough triangles on parchment lined cookie sheet and bake for 18 to 20 minutes rotating the baking sheet halfway through, or until a toothpick inserted into the center of a scone comes out clean. Do not overbake. Transfer the scones to a wire rack to cool completely.
When ready to serve, soften the remaining Nutella in the microwave for about 5-10 seconds and drizzle it on top OR pipe it out of a freezer bag with the corner snipped off.