If you haven't already, soak the pitted dates, either in hot water for 10+ minutes or overnight in water in the fridge.
Line a loaf pan with parchment paper.
In a food processor, pulse the walnuts into a very fine crumb, scraping down the sides partway through if needed.
Add the hemp seeds and dates, processing until the mixture is as smooth as you can get it. The mixture will be very sticky and you will need to stop several times to spread it out again and scrape down the sides.
Add the cocoa powder, vanilla extract, and sea salt to the food processor. Use your spatula to mix the cocoa powder into the date mixture a little bit so that it doesn't fly everywhere when you run the processor again. Blend until well combined. Add maple syrup as desired to adjust the sweetness level.
If using, melt the chocolate chips and nondairy milk together over indirect heat, stirring constantly to incorporate them together. Pour the mixture into the food processor and add the cacao nibs if using. Pulse a few times to swirl in the chocolate.
Transfer the mixture into the loaf pan and smooth it out as much as possible. It will be very sticky so it may be difficult to get it completely smooth.
Freeze for at least 30 minutes before slicing and serving. The fudge should slice very easily straight from the freezer with a sharp knife, and tastes best when eaten cold.
Store leftovers in the freezer in an airtight container.