Blend the hazelnuts in a blender for a few seconds. You should get a coarse hazelnut powder.
Add the hazelnut powder to a bowl, then sift in the chestnut flour.
Mix with a spoon, then add sugar, coffee, soy milk, hazelnut chocolate spread, and rum (optional).
With a silicone spatula, or with a spoon, mix the ingredients together. You can also mix with your hands to be faster.
Mix till you get a compact dough, that is a little sticky. It should take a couple of minutes.
Divide the dough into small pieces of about 22 grams each. I like to use a scale here. That is the best weight to make these truffles bite-size. You should be able to get about 25 pieces.
With the palms of your hands, shape the dough pieces into smooth balls.
On a small plate add the cacao powder, on another small plate add the shredded coconut. Roll each ball into either the cacao powder or the shredded coconut.
Set aside on a serving plate and serve. If you don't serve them immediately you can put them in the refrigerator for up to 3 - 4 days.