2. Spray 8 ramekins with cooking spray and sprinkle them with the 2 tablespoons of granulated sugar.
3. Combine flour and salt in a small saucepan. Gradually whisk in the milk. Bring to a boil over medium heat, whisking constantly, and cook until thick, about 3 minutes.
4. Remove from heat and let cool for a few minutes. Whisk in the instant coffee, vanilla and egg yolks. Add the chopped chocolate and stir until it is melted. Transfer the chocolate mixture to a large bowl and set aside.
5. Place the egg whites and cream of tartar in the bowl of an electric mixer and whisk on high speed until the eggs are foamy. Gradually add half of the granulated sugar and beat until stiff peaks form. Continue beating and slowly add the remaining sugar.
6. Gently fold 1/4 of the egg white mixture into the chocolate mixture. Fold in the remaining egg white mixture. Spoon the batter into prepared ramekins. Bake for 20 minutes or until puffy and set.
7. Sprinkle with powdered sugar and serve immediately.