In a food processor combine the dry ingredients and pulse.
Add the wet ingredients and blend to combine. The mix should stick together in the food processor, but not be so moist it forms a ball. If you think it needs more liquid, add 1 tsp at a time, process and add more if needed.
Pulse through 1/2 the walnuts right at the end.
Line a small square baking dish or storage container with a parchment paper -- mine was L 18cm x W 11cm
Press the brownie mix into the dish and smooth it down with the back of a spatula or a spoon.
Chop the remaining walnuts roughly and press into the top of the brownies.
Pop in the fridge or freezer to set, about 10-20 mins.
Cut and serve or store in an airtight container in the fridge for up to 2 weeks or in the freezer for several months.