Position rack in center of oven and preheat to 350°F (180°C).
Spray 8 ramekins (5-oz./160ml cap.) with nonstick baking spray. Set aside.
Pour cake mix in large bowl. Set aside.
In small saucepan over medium heat, combine butter and water, then bring to a boil. Continue heating, stirring occasionally, until butter has melted, approx. 3 minutes.
Pour butter mixture over cake mix in bowl and whisk together until smooth and most chocolate pieces have melted, approx. 2–3 minutes.
Pour batter into prepared ramekins, using approx. 1/2 cup per ramekin. Place filled ramekins on half-sheet pan, spaced evenly apart. Bake until tops of cakes are set and firm, approx. 18 minutes. Do not overbake.
Transfer half-sheet pan to wire rack and let cool for 15 minutes. Run small knife around inside edges of ramekins to loosen cakes. Turn cakes out onto individual dessert plates.
Dust with confectioners' sugar and serve immediately with whipped cream or vanilla ice cream, if desired.

Williams Sonoma Peppermint Chocolate Molten Cake