Preheat oven to 160 ℃ or 325 ℃ . Grease an 8 inch square pan with butter , dust with flour and line the bottom with parchment .

In a saucepan , heat chopped chocolate , cubed butter and milk together until the chocolate n butter have melted. Keep warm.

Whisk together the flour, salt and baking powder . Keep aside.

Using an electric mixer or whisk, whip the eggs with the sugar and vanilla until triple in volume and pale in colour . If you lift your beater or whisk and draw an eight on the top of the batter , you should be able to see the whole 8 before it disappears.

Add the flour mixture and beat on low until combined.

Add the chocolate-butter-milk mixture and beat until smooth.

Pour batter into prepared pan .

Bake for 45 to 48 minutes until a toothpick inserted in the centre comes out dry. The top will be golden brown and edges will be coming away from the sides.

Cool in pan for ten minutes and gently unmould. Cool completely.