In a microwave safe bowl, melt the chocolate in your microwave. Make sure you set your microwave for small increments of time, so the chocolate doesn’t boil or overflow. Trust me this CAN happen…..I set my microwave, walked away and came back to a giant mess of chocolate all over the inside of my microwave.
Once your chocolate is melted, add the Nutella and hazelnuts. Using one of the above options, melt the bittersweet chocolate. Using a small pastry brush gently brush the inside of the candy cups with the bittersweet chocolate. If the bittersweet chocolate starts seizing up rewarm it as necessary so it’s easy to spread. You won’t use all the chocolate, so set the remaining bittersweet chocolate aside. Place all the cups on a baking sheet or sheet pan and refrigerate until the chocolate is firm, about 15 – 20 minutes.
Once the chocolate cups are ready, spoon a heaping spoonful of the chocolate hazelnut mixture into each cup. You want the cups to be pretty full up to the top of the cup. Put the chocolate filled cups back in the refrigerator until the filling is set and firm, about 15 minutes.
Gently reheat the remaining bittersweet chocolate and spoon enough over the filling in each cup to fill the cups completely. Immediately (before the melted chocolate can set) place one hazelnut on top of each truffle. Put the cups back in the refrigerator until the chocolate is set and very firm, about 20-30 minutes. Before serving, let stand at room temperature about 15-20 minutes.
These can be made up to 2 weeks ahead. Just make sure you refrigerate them in an airtight container.