Preheat oven at 180°C.

Butter a 10'X8' rectangular baking pan

In a double boiler oven low heat, melt butter and choco chips together and remove from heat

In separate bowl, combine dry ingredients

When chocolate/butter mixture has cooled completely, whisk in the eggs and vanilla(Note: It is important to cool the chocolate/butter mixture completely or the eggs will curdle)

Seive together all the dry ingredients and whisk in the chocolate mixture

Add chopped walnuts

Pour the batter in the pre heated pan, and bake for 35-40mins

Cut into brownie square once cooled