Preheat oven to 395F.
Fill a 1 cup measuring cup halfway with dates and add just enough boiling water to cover. Let dates soak for about 10 minutes, while preparing the rest of the ingredients.
Place black beans, oats, cocoa powder, peanut butter, and vanilla in a food processor. Add the dates along with the soaking water and process until smooth, and there aren't big chunks of dates.
Using a spoon, divide the batter into 12-24 cookies on a baking sheet lined with a silicon mat or baking paper.
Bake for 10 minutes, then remove and let them cool on a cooling rack.
For the filling, combine equal parts nut butter and date syrup - about 2 tablespoons of each. The consistency of nut butter can vary, so if the filling is too thick, add a tiny dash of soymilk and if it's too runny add a little bit of cocoa powder.
Sandwich the cookies together using the filling and enjoy!