Preheat the oven to 425F. Butter and sugar a large soufflÄ mold. Break the chocolate into small pieces and place in the top of a double boiler with the 2 tablespoons of sugar, vanilla extract, and 1 tablespoon of water. Melt over barely simmering water. Remove from the double boiler and whisk in the egg yolks, 2 at a time. Beat in half of the sugar and the potato or cornstarch. In a copper bowl whisk the egg whites until stiff. Beat in the remaining sugar, 2 tablespoons at a time. Fold the egg whites into the chocolate mixture until uniformly mixed. Fill the soufflÄ mold to the top of the rim and run your finger around the inside top edge, making a small indentation. Bake for 25 minutes. Serve immediately, sprinkled with confectioner╒s sugar.
