Blend dates, black beans and plant based milk till completely smooth. Add the rest of the ingredients for the batter except walnuts and chocolate chunks and process till incorporated. Lastly add walnuts and chocolate chunks and pulse a few times. Pour the mixture in your prepared tin(use a parchment on the bottom for an easy removal) and bake for 25 minutes, allow to cool completely before removing from the tin, if you want to frost it.
For the frosting:
Blend all the ingredients together till completely smooth and place in the fridge, while brownie is cooling.
When ready to frost, take your brownie layer and gently with spatula spread your frosting across.
I like to leave them on the fridge to set completely and for the frosting to merry the brownie.