In a small bowl blend together Nutella and rum until Nutella is dissolved. Slowly stir in heavy cream.
Add powdered sugar and Gingerbread spice and whisk until sugar has dissolved. If there are lumps, strain the mixture through a fine-mesh sieve or cheesecloth. Alternatively, combine all ingredients in a blender.
Fill clean glass bottles and refrigerate overnight to allow for flavors to blend. Store in the refrigerator for up to two months. Shake well before using.
This recipe can be easily doubled or even tripled.