1 Add walnuts and cashews into a blender or food processor. Process for 2-3 minutes on high speed until you reach a fine consistency. Add in cacao and salt and process again until well incorporated.
2 Add in Medjool dates and vanilla and process until dates have broken down.
3 Slowly pour in the maple syrup until you reach a sticky fudgy mixture (will probably form a ball in the food processor, that's when you know you're done).
4 Press into a lined cake tin and sit in the fridge.
5 In the meantime, add all frosting ingredients into a high speed blender and blend until smooth and creamy. Take out brownie mixture and pour on top, using a spoon or spatula to evenly distribute the frosting on top.
6 Return to the fridge for an hour before slicing up and serving. Top with crushed walnuts & a pinch of sea salt if desired.