2 tablespoons unsalted butter
1 tablespoon sugar
1/4 cup sugar
2 tablespoons hazelnut-flavored liqueur
1/2 teaspoon vanilla
3 ounces dark chocolate
6 ounces milk chocolate
1/4 cup all-purpose flour
1 cup milk
1 pinch salt
4 eggs, separated
1/4 teaspoon cream of tartar
Preheat oven to 375°.
Butter and sugar 6 ramekins.
Heat the butter, 1 tablespoon sugar, hazelnut liqueur, and vanilla in a double boiler over medium heat until the butter melts.
Remove mixture from heat, add the dark chocolate, and let it sit until melted, about 3 minutes.
Place mixture in the freezer for 10 minutes to allow it to set. Use a spoon to form mixture into 6 even balls. Reserve in the refrigerator.
Place flour in a double boiler and slowly whisk in the milk. Add salt.Whisk mixture over heat until thick, about 5 minutes. Add yolk and continue to mix constantly until it is about the consistency of mayonnaise.
Remove from heat and add chocolate, allowing it to melt.
Place egg whites and cream of tartar in a bowl and whip with a hand mixer until they form soft peaks.
Gradually add remaining sugar and whip until hard peaks are formed. Fold egg whites into warm chocolate mixture. Place ball of chocolate filling in each ramekin. Fill each ramekin to the brim with souffle mixture. (At this point, they can be covered and refrigerated for up to two days).
Place ramekins in a water bath and bake until golden brown on top, about 30 minutes (40 if refrigerated).