For the soufflé base:
For assembling and baking soufflé
Begin by preheating the oven to 350 degrees. Butter six 4oz ramekins and coat them with the 2 tbsp of sugar. Place them on a sheet tray.
To make the base: Scald the milk and espresso beans in a heavy bottomed pot. Remove from heat and let steep for 15 minutes. Place the egg yolks in a bowl and whisk in the sugar; stir in flour and salt. Strain the espresso milk into the egg yolk mixture. Place the bowl over a simmering double boiler and whisk constantly for 2 minutes until the mixture thickens. Remove from heat, cover directly on surface with plastic wrap and refrigerate until cold.
For assembly and baking: Using an electric mixer, whip the egg whites in a large bowl until foamy. Add the cream of tartar and salt. Whip to stiff peaks. Fold the soufflé base into the egg whites and immediately spoon evenly into the ramekins and give each one a little tap on the counter to pop any large bubbles. Place on the middle rack of the oven. Close door gently. Souffles will begin to rise after 10 minutes and should be well risen and ready by 15 minutes.
Dust with powdered sugar and serve immediately.