If your dates are a little dry, add them to a bowl of warm water for 5-10 minutes.
Blend walnuts and cashews in food processor until they are the consistency of flour. Next add in almond flour, cacao powder and salt and process until mixed.
Add dates (drained, if you had them soaking) and vanilla to food processor mixture and blend until mixed well. You may need to add 1-2 tbsp of water if your dates aren't moist enough. The dough should stick together when pinched.
Transfer dough to lined loaf pan.
In a medium sized bowl, mix together cashew butter, maple syrup and coconut oil until well combined. Pour over dough and place in fridge to set for at least 2 hours.
Once set, cut into 8 bars and enjoy!