Add the cashews, dates, cashew butter and vanilla to a food processor. Process until the mixture sticks together when pressed.
Add the cocoa nibs and pulse a few times to combine.
Transfer the cookie dough mixture to a mini muffin pan. If you don't have a pan for mini muffins, you can make larger cups.
Press the cookie dough mixture to make 12 small cups. Place in the refrigerator while you make the chocolate mousse.
Make the chocolate mousse: In the same food processor (no need to clean it, but remove crumbs), add all the mousse ingredients. Process until smooth, 4-5 minutes (or longer, depending on the strength of your food processor). The mixture should be lightly thick.
Scoop the chocolate mousse into each cookie dough cup. There should be some mousse leftover. Top each cup with a sprinkle of cocoa nibs if desired.
Place the cups in the freezer for at least 20 minutes until the filling hardens or store it in the refrigerator until ready to serve.