In a sauce pan, over medium low heat, bring the heavy cream and butter to a simmer, while whisking constantly. Simmer until tiny bubbles appear around the sides of the sauce pan.
Remove from heat and immediately add the chopped chocolate. Stir into the cream and butter mixture until the chocolate is melted.
Add the nutella and stir to combine. Place in refrigerator for 2-4 hours to chill.
While the truffle mixture is chilling, prepare a two shallow bowls - one with sprinkles, and one with nuts. (You can also roll in cocoa powder, toasted coconut, or anything else you can creatively think of!)
Once the truffle mixture is ready, portion out one teaspoon using a small cookie scoop. Roll into a ball and roll into the coating/topping of choice. Transfer to a plate or baking sheet. (I like to place them right into mini paper muffin liners if I happen to have some on hand.)
When all truffles are done, refrigerate to firm up. If you find the truffle mixture is getting too warm or soft during the rolling stage, place the mixture back in the fridge for a few minutes to firm back up.