Preheat oven to 375 degrees F and place the rack in the center. Line a baking sheet with parchment paper. In a large bowl - whisk the flour, sugar, cocoa powder and salt until combined Add the butter. Use your fingers to rub it into the flour until the butter is pea sized and the mixture is coarse. In a separate bowl - whisk together the egg and heavy cream until combined. Slowly pour into the dry ingredients and stir until the dough just comes together. Gently knead the dough with your hands. Add the hazelnuts and knead gently to incorporate. Flatten the dough into a rectangle approximately 6 x 12 inches and spread 1/4 cup of the Nutella on top in a criss-cross pattern. Roll the dough up to make a cylinder a bout 6 inches long, turn on its end and flatten it into a disk about 1 3/4 inches high. DO NOT OVERWORK THE DOUGH. Cut the dough into 6 or 8 wedges and place on the prepared baking sheet. Bake for 18-20 minutes, rotating the baking sheet halfway through, or until a toothpick inserted into the scone comes out clean. Transfer the scones to a wire rack to cool completely. Place the baking sheet with the parchment paper still on it underneath the rack. Before serving: Heat the scones in a microwave Heat the remaining 1/4 cup Nutella Ina a microwave until pourable. (About 10 seconds on high). Pierce the scones several times with a fork. Using a spoon drip the warm Nutella in a zigzag pattern over the hot scones. Transfer to the refrigerator to cool and set for 5 minutes and serve immediately. Wrap tightly and store at room temperature.