Pre heat the oven to 350 degrees F.

Butter the inside of 9 ×13 inch baking pan and line with parchmet paper.

Again grease it with butter.

Mix flour, salt and coco powder.

Sift twice to avoid lumps.

Now over a double boiler melt chocolate chunks and butter together.

Cut butter into small cubes too.

Stir well until everything is melted.

Turn off the heat and whisk in both sugars till its all well combined.

Now take it off the flame and add eggs one by one. Whisk it properly after every egg added.

Add vanilla essense and mix it well.

At the end add flour and coco powder mixture into the chocolate batter in portions and fold with batter in portions and fold with a rubber spatula till it is well combined.

Fold in the chocolate chips and walnuts at this point if u want.

Now pour this batter in the baking pan and bake for 30 minutes or util the tooth pick inserted in the center of the brownies comes out with little moist crumbs.

Take it out and let it cool down completely.

Cut into squares and serve on room temperature.