Pre-heat oven to 175 C non-fan (160 C fan forced). Line a 33 cm x 23 cm baking tray with double layer of foil or baking papers with sides extended. Grease the inside if using foil.

In a medium bowl, mix flours, baking powder and salt to distribute the baking powder through the flour. Set aside.

In a large bowl add just-boiled water, finely chopped chocolate, cocoa powder, oil, instant coffee and vanilla. Mix well with whisk until chocolate is melted.

Using a rubber spatula, stir in sugar till fully combined.

Add chocolate bits and chopped walnuts and stir to incorporate. Spoon into the prepared baking tray and level top. 

Bake in preheated oven for 20 – 25 minutes for a fudgy centre with a crunchy top, longer if you like a more baked brownie.

Allow to completely cool in the baking tin (several hours,) then cut into serving squares and enjoy. 

The brownies keep well at room temperature for 4 -5 days.