In a medium to large microwave-safe bowl, melt the chocolate hazelnut spread for 15 to 20 seconds, until it's soft and pliable. Stir in liqueur. The spread will become a paste of sorts, similar to the consistency of chilled chocolate ganache; this is perfectly normal. 

Fold in Rice Krispies and mix with hands to make sure everything is fully incorporated.

Roll the “truffle” mixture into bite-size balls. Save any crumbly Rice Krispie bits aside for garnish.

Once the truffles have set, dip them in melted chocolate, then set them on parchment paper to harden. Sprinkle with any reserved Rice Krispie bits.

Allow to set for about an hour before eating.

Variations:

If you are not a fan of Nutella, swap it for peanut butter and omit the hazelnut liqueur. Also, add a couple tablespoons of maple syrup to enhance the sweetness, if desired. Additionally, you could also roll the truffles in milk or white chocolate if you prefer those to dark chocolate.