Pit the dates if they have pits, then roughly chop them to make blending easier. Place the chopped dates into your food processor.
Pulse the dates in the processor until they break down into a sticky, caramel-like paste, about 30 seconds, scraping down the sides as needed.
Add the sifted cocoa powder, a tiny pinch of sea salt, and vanilla extract to the processor. Blend until the mixture is smooth and evenly combined, about 20 seconds.
Transfer the mixture to a mixing bowl. Coarsely chop the nuts or pulse them briefly in the processor, then fold them into the chocolate-date mixture for added crunch.
Line a small pan (about 20x20cm) with parchment paper, then scoop the mixture into the pan. Using a spatula or your fingers, press it evenly into the pan, about half an inch thick, making sure to pack it tightly.
If desired, sprinkle extra nuts or cocoa on top, pressing them gently into the surface for a decorative finish.
Place the pan in the fridge and chill for at least 30 minutes until the mixture is firm and easy to cut.
Once chilled, lift out the mixture using the edges of the parchment paper and transfer to a cutting board. Slice into 12-16 squares or rectangles with a sharp knife.
Serve immediately, enjoying the dense, fudgy texture and rich chocolate-caramel flavor, or store in an airtight container in the fridge for up to a week.