Prep Time: 10 minutes, plus 10 minutes cooling
Cook Time: 25 minutes
Make-Ahead: The batter can be made up to 1 day ahead, covered and refrigerated. Allow a bit more baking time when using the cold batter.
Preheat the oven to 375°F. Brush the interior of a 1-quart Curtis Stone Hot and Steamy Pudding Cake Mold with softened butter. Refrigerate the bowl for about 5 minutes, or until the butter is firm. Dust the mold with flour and shake out the flour. Tap the mold upside down on a flat work surface to remove any excess flour. Refrigerate the mold.
In a large bowl set over simmering water, heat the chocolate until melted. Add the 9 tablespoons of butter and whisk until smooth. Remove the bowl from the heat and set aside.