Preheat the oven to 180°C (approximately 350°F). Melt the chocolate and butter over a hot water bath. Separate the eggs. Stir the egg yolks and sugar into the chocolate mixture. Mix the flour, salt and coffee. Mix into the chocolate mixture. Beat the egg whites until stiff and fold into the batter. Pour into a buttered springform pan and bake for 25-30 minutes. The brownie should be moist in the middle. Remove from the oven, let cool and serve.