Add all of the ingredients for the fudge to a small saucepan and heat over medium, stirring constantly, just until all ingredients are well-combined, and the mixture is very thick.
Transfer the fudge mixture to the prepared loaf pan and smooth into an even layer.
Sprinkle fudge with sunflower seeds, sesame seeds, cacao nibs, and chopped walnuts. Gently press the toppings into the fudge. Freeze (uncovered) for 2 hours, or until fudge has solidified.
When ready to serve, allow fudge to thaw 10 to 15 minutes, then cut into small squares using a sharp knife. Store fudge in a sealed container or bag in the freezer or refrigerator.