Place 8 ounces of semi-sweet chocolate in a large heatproof bowl. Microwave in four fifteen second increments, stirring after each, for a total of 60 seconds. Stir until almost completely melted. Set aside.

Pour cream into a small saucepan over medium heat. Whisking occasionally, heat until it just begins to boil. Remove from the heat, then slowly pour over the chocolate. Gently begin stirring with a wooden spoon in one direction. Do not forcefully stir, always be gentle! Once the chocolate and cream are smooth, stir in the Nutella and butter until combined and smooth, then stir in 1/2 cup of the hazelnuts. Cover with plastic wrap pressed on the top of the mixture then allow to sit at room temperature for 15-30 minutes. Then place in the refrigerator until it reaches “scoopable” consistency, about 4 hours.

Line a lage baking sheet with parchment paper or a silicone baking mat. Set aside.

Remove mixture from the refrigerator. Measure 1 teaspoon, roll mixture in your hands into a ball as best as you can, then place on the baking sheet. The mixture will be a little sticky. Coat your palms with a little cocoa powder, which I find helps you handle the mixture. Repeat rolling the rest of the mixture. (A rolling tip: If you can’t roll into perfect balls, do the best you can and place on the baking sheet. The air will help “dry out” the truffles. After 15 minutes, you’ll be able to roll them into neater balls.)

You can melt the remaining 8 ounces of chocolate in a double boiler or the microwave. (Alternatively, you can temper the chocolate.) If using the microwave: place the chocolate in a medium heat-proof bowl. I like to use a liquid measuring cup. Its depth makes it easier for dipping. Melt in 15 second increments in the microwave, stirring after each increment until completely melted and smooth.

Dip each truffle completely into the chocolate using the spiral dipping tool or a fork. When lifting the ball out of the chocolate, remember to tap the dipping tool gently on the side of the bowl to allow excess chocolate to drip off. Place balls back onto the baking sheet after you dip each one. Drizzle with any leftover chocolate. Sprinkle with remaining hazelnuts. Refrigerate for 30 minutes or until chocolate has completely set before serving.