If you dates are a little older, I suggest soaking them in hot water for about an hour. Before using, drain out the water.
Combine the dates and water in a blender or food processor. Process for 1 minute, scrap down the sides and blend more until smooth and creamy with very few lumps remaining. I suggest stopping the processor about every 30 seconds to scrap down the sides. All together, it could take about 4 minutes.
If using the cocoa powder, add it at the end and bend until fully combined.