Powder 2 tbsp of flax seeds and add into a small bowl.
Add 1/4 cup of water to flax powder, mix and keep aside for 15 minutes. This will be our flax egg.
Take a bowl and add oil, sugar, milk and flax egg. (See notes below)
Whisk them so well.
Add all the 3 flours. (see notes)
Also add baking powder, salt and cocoa powder.
Mix them well.
Now add a tsp of any of the flour from amongst the 3 to the roughly chopped walnuts. Coating the walnuts with flour prevents the walnuts from sticking to the bottom of baking tin.
Add walnuts and vanilla essence.
Give it another mix.
Transfer the batter into a baking tin greased with lined butter paper.
Level the batter with spatula and tap the tin to release any extra air.
Bake in preheated oven @180°C/356F for 30 to 35 minutes in the middle rack with both the rods on.
After the said period, take the tin out of oven and insert a toothpick in the brownie. If the toothpick comes out clean, it means brownie is perfectly baked.
Let it cool down completely.
Brownie is ready. Invert, cut into pieces and enjoy.