Preheat the oven to 325°F or 160°C.
In a heatproof bowl, melt chocolate and butter together.
Let the mixture cool completely at room temperature.
Melt chocolate and butter together, on a double boiler or in the microwave. Double broiler method is more reliable as in microwave mixture can heat up more thus breaking the chocolate structure or overheating of butter.
Mix eggs, sugar, and vanilla essence together until well blended. We don't have to beat the eggs, it will give us more crumbly, and less fudgy brownie.
Blend in the egg mixture with the chocolate-butter mixture.
Sift in the flour and fold.Fold in the nuts dusted with little flour.You can sprinkle additional 50g chopped nuts or chocolate chips on the batter after panning.
Bake in a square pans for 40-45 minutes at 325°F or 160°C. Baking time may differ depending on the oven and the pan used. I used 7"X 7" pan, it took exactly 40 minutes to bake.
Once baked, leave the pan on the counter, once it cools completely cut into square pieces.