Preheat your oven to 300 and line a baking sheet with parchment paper.
Combine the melted butter, egg, stevia and vanilla extract in a large bowl and set aside.
Add the walnuts to a processor and pulse until ground. Pour walnut flour into a medium bowl and add the coconut flour and 1/4 cup of the swerve. Combine.
In two parts add the dry mixture to the wet and whisk to combine.
At this point the dough should be soft, but firm enough to form into balls by hand without it sticking to your palms. If it is not the right consistency add 1-2 tbsp of additional coconut flour and combine.
Make 15 equal sized balls and line the parchment paper. They will not spread in the oven. Bake for 30 minutes.
Allow to cool for 5 minutes, and then roll the (still warm) balls in the remaining 1/4 cup swerve. Place them back on the parchment paper and allow to fully cool, another 20-30 minutes, until eating!