- With the rack in the middle position, preheat the oven to 350°F (180°C). Butter an 8-inch (20 cm) square baking pan and line the bottom with a sheet of parchment paper, letting it hang over two sides.
- In a bowl, over a double boiler or in the microwave oven, melt chocolate with butter. Let cool.
- In another bowl, combine eggs, brown sugar and salt with a whisk until the mixture is smooth. Add chocolate mixture and flour and stir until smooth. Pour into the prepared pan.
- Bake for about 23 to 25 minutes or until a toothpick inserted in the centre comes out with a few lumps and not completely clean.
- Let cool in the pan, about 2 hours. Remove from pan and cut into squares. Serve warm or cold.