Preheat the oven to 325 (F).
Put 6 1/2 oz. chocolate and 1 1/2 sticks butter in a large, heatproof, stainless steel bowl over a saucepan of simmering water -- make sure the base of the bowl does not touch the water. Leave until melted and smooth, stirring occasionally.
Remove bowl from heat. Add 1 2/3 cups sugar, and use a rubber spatula to stir the sugar into the chocolate and butter mixture until well incorporated.
Add 1 cup flour and stir until just incorporated. There should be one or two flour streaks left -- be careful not to overmix, or your brownies will be too tough and I will be sad.
Finally, stir in the eggs and mix until just incorporated. The batter should be thick and smooth at this point.
Spoon the dough into the prepared baking pan and bake in the preheated oven for about 30-35 minutes, or until flaky on top but still soft in the center. Be careful not to overbake otherwise the edges will become hard and crunchy.
Let cool completely on a wire rack before dusting with confectioner’s sugar to decorate.