Take an oven and position the rack in its center

Preheat to 350 degree F

Take a 8-inch-square baking pan and line it with foil and hang it on two opposing sides. This should be coated with cooking spray

Sift the cocoa, confectioners' sugar and flour together into a small bowl

Mix it with 3 ounces chopped chocolate and oil in a heavy medium saucepan

Put the pan at the lowest heat and keep stirring it until it is just melted and smooth

Make sure the chocolate does not overheat

Once the heat is done remove the mix and stir it in corn syrup mixture, granulated sugar, salt and vanilla until the sugar dissolves

This should be later stirred in egg vigorously until it is smoothly incorporated

And then stir it gently mixing the dry ingredients

Take the remaining 2 1/2 ounces chopped chocolate and fold the walnuts till it is well blended

Turn out the batter into the pan and spread it evenly

Bake the brownies till they are firm in the center 

When a toothpick is inserted, it should come out with some moist batter clinging to it say for about 20 to 24 minutes

Leave it for cooling down completely on a wire rack for about 2 1/2 hours 

Use the overhanging foil as handles and carefully lift the brownie slab from the pan

Peel the foil from the bottom and set the slab right-side up on a cutting board

Take a large, sharp knife and trim off any dry edges

The slab must be cut cross-wise into fifths and lengthwise into fourths

The blade must be wiped with a damp cloth between cuts

The brownie can be served with a scoop of vanilla ice-cream and hot melted chocolate