Preheat the oven to 175 degrees Celsius. Grease the bottom and sides of an 8x8-inch baking tin and line with baking parchment, leaving an overhang so that it is easier to lift out the brownie when it has cooled.
Melt the chocolate and butter in a double boiler. Set aside for 10 to 15 minutes to let the mixture cool slightly. Whisk in the sugar, vanilla and egg whites then stir in the flour, cocoa powder and salt.
Spread half of the batter evenly on the baking tin. Place the cream cheese slices on top of the batter, arranging the slices as close to each other as possible. Spread the remaining batter over the cream cheese slices.
Bake for 15 to 20 minutes until the top is dry but a skewer inserted into the centre of the cake comes out damp. Set the tin on top of a wire rack and let the brownies cool completely in the tin. Lift out the brownies using the baking parchment overhang, though it's a lot easier to lift out if the brownies are chilled first in the refrigerator.
Slice the brownie into 16 slices, dust with icing sugar and serve.