Preheat your oven to 180 degrees C and line an 8 or 9 inch square pan with parchment or foil. Make sure at least 2 opposite edges have extra overlapping to lift them out later.

Melt the chocolate and butter together in the microwave . You could also melt it in a saucepan , stirring continuously so it doesn't burn

Whisk in the sugar .

Whisk in the eggs , ONE BY ONE. Beat well after each egg.

Whisk in the vanilla.

Add in the flour and salt . Mix until no flour can be seen. The batter will be thick

Spread it as smoothly as possible. Bake at 180 C for 35-40 minutes if you using an 8 inch pan, 30-35 minutes if using a 9 inch pan. The brownie will come away from the edges and a toothpick inserted in the centre will have only a few moist crumbs

Cool completely in the pan on a rack. Lift out the parchment /foil and cut!