Preheat oven to 350°F.
Butter 1-quart souffle dish and dust lightly with sugar, shaking out excess.
Set dish aside.
Combine milk, liqueur, coffee powder, Cognac, chocolate and vanilla in medium saucepan over low heat and cook, stirring frequently, until chocolate is melted.
Remove from heat and set aside.
Melt 1/4 cup butter in 2-quart saucepan over medium heat.
Add flour and stir until bubbly.
Gradually add chocolate mixture, sugar and salt, whisking constantly until smooth.
Bring to boil and cook until thickened, about 2 to 3 minutes.
Turn into large bowl.
Add egg yolks 1 at a time, whisking until well blended.
Beat egg whites in another bowl until stiff and glossy.
Stir large spoonful of whites into chocolate mixture to lighten.
Fold in remaining whites until completely incorporated.
Gently spoon into prepared dish, mounding slightly in center.
Bake until tester inserted near center of souffle comes out clean, about 25 minutes.