Chop the nuts and goji berry into tiny pieces and mix together.
In a small bowl combine the coconut oil, stevia powder and cocoa powder. If the coconut oil is hard, microwave it for a few seconds first.
Wait until the chocolate sauce cools down has the consistency of honey before dipping the donuts in it. If it's winter, it should take a couple of minutes on the countertop, but if it's summer, you'll need to refrigerate it for a few minutes.
Once thick, dip the top of each donut into the chocolate sauce. Immediately top with the chopped nuts while the chocolate sauce is still runny so that they can stick. Once coated, let them cool on the counter (in winter) or in the fridge (in summer).
*If the chocolate sauce hardens up, just microwave it for 3-5 seconds until it's soft again.