Grease an 8x8 baking pan with coconut oil. Line with parchment paper.
Place dates, hemp seeds, walnuts, cocoa powder, salt, vanilla extract, and water into bowl of a food processor. Process until smooth, stopping occasionally to wipe down sides.
Transfer mixture to prepared pan. Press down into pan in an even layer using a piece of parchment. The "batter" will be sticky.
In a small bowl, combine chocolate ganache frosting ingredients. Whisk until smooth.
Spread frosting over brownie layer. Place baking pan in freezer for at least two hours until set.
Remove brownies from pan using parchment flaps and cut into small squares on a cutting board. Store in an airtight container in the refrigerator.