Line an 8-inch square pan with parchment paper.
In a medium pot, combine the dates and water. Bring to a boil, then simmer for 5-10 minutes until the dates are soft.
Transfer the mixture to a food processor. Add maple syrup, vanilla, cocoa powder, and salt. Process until smooth.
Add the oats and chopped nuts, pulsing until evenly combined.
Spread the mixture evenly into the prepared pan. Press down firmly.
Chill in the refrigerator for at least 1 hour to firm up.
Optional: Drizzle with melted dark chocolate before cutting into bars.