Place 1 cup walnuts and the almonds in food processor and process until finely ground.
Add the cacao powder and sea salt and pulse to combine. Transfer to bowl and set aside.
Add the dates to the food processor and process until small bits remain. Remove and set aside.
Add nut and cocoa mixture back into food processor and while processing, drop small handfuls of the date pieces down into the food processor or blender spout.
Process until a dough consistency is achieved, adding more dates if the mixture does not hold together when squeezed in your hand. You may not use all the dates.
Add the brownie mixture to a small parchment lined 8x8 dish and before pressing, add remaining 1/2 cup roughly chopped walnuts and cacao nibs and toss to combine and evenly distribute. Then press down with hands until it is flat and firm. Laying down a piece of plastic wrap to prevent sticking and get it really flat.
Lift parchment paper to remove brownies from dish and use hands to slightly squash in the sides to create a smaller square - this will make the brownies slightly thicker and more dense.
Transfer back to dish and place in freezer or fridge to chill for 10-15 minutes before cutting into 12 even squares (If adding ganache, slice afterwards!).
FOR THE GANACHE:
Add almond milk to a mixing bowl and microwave for 45 seconds or until very warm. Alternatively, heat in a small saucepan until just simmering, then transfer to mixing bowl.
Immediately add chocolate to warm milk and loosely cover. Don’t touch for 2 minutes so it can melt.
Add salt and stir gently with a wooden spoon to incorporate, then add melted coconut oil and use a whisk to mix. Set in fridge for 10 minutes to thicken.
Remove from fridge and add powdered sugar a little at a time to thicken. Whisk again to combine. If it’s still too thin, add another few Tablespoons powdered sugar and beat until light and fluffy.
Frost brownies generously with frosting and then top with additional raw walnuts and cacao nibs (optional). Slice into 12 even squares.
Store brownies in an airtight container to keep fresh. Will keep for 3-4 days at room temperature, or in the freezer for at least 1 month (though best when fresh).