It would be a disaster to underbake most cakes. In this recipe, though, that's the secret to making the delicious molten chocolate center that gives the dessert its name. Baking in small batches gives you and young chefs the time to perfect technique and timing. For perfectly melted chocolate, check out our dos and don'ts.
Heat the oven to 450°. Use a double boiler or create your own by filling a saucepan with an inch of water, then fitting a heat-safe mixing bowl in the top of the pan. Combine the butter and the chocolate in the bowl over hot (but not boiling) water, stirring occasionally, until the chocolate is melted, about 5 minutes.
When it is completely melted, stir or whisk the chocolate mixture to fully combine the ingredients. Remove the bowl from the saucepan and stir in the vanilla extract. Set it aside.
While the chocolate mixture cools, butter six (8-ounce) ceramic ramekins or custard cups (the sides of each cup should measure no taller than 2 1/4 inches). Place 1 teaspoon of granulated sugar inside each one. Tip and turn the cups to coat them with the sugar, then set them aside.
In a large mixing bowl, whisk the eggs and egg yolk. Add the confectioners' sugar, and whisk again. The mixture will look lumpy at this point, but it will become smooth as more ingredients are added. Whisk in the chocolate mixture, then add the flour and salt, and stir with a wooden spoon until the batter is smooth.
Divide the batter among the 6 baking cups and set 5 of them aside. You'll use the sixth cake to conduct a trial run of the baking process.
Place your trial cake in the coolest part of the oven and bake it until the top is flat (not sunken or bulging), about 9 minutes. Be sure to monitor the baking closely so that the cake does not overbake and become set in the center.
Remove the trial cake from the oven -- making note of your exact baking time -- and place it on a potholder to cool for 5 minutes. Run a sharp knife around the perimeter of the cake to loosen it from the baking cup.
Place a dessert plate over the baking cup and, using the potholder, invert the cake onto the plate. Wait 10 to 15 seconds, then carefully lift the cup off the plate. The cake should have a nice, round shape and be slightly sunken in the center. Use a knife to gently poke the middle of the cake to find out if it's molten and lavalike beneath the surface.
Finish baking the cakes in two batches, adjusting your baking time up or down in one-minute increments as needed. Serve the cakes at room temperature (they need about 30 minutes to cool) with whipped cream or a scoop of vanilla ice cream. We recommend splitting each cake into two servings, as they are quite rich. Makes 6 mini cakes.
Keeping Your Lava Cakes Dormant: As irresistible as these cakes are, you don't have to eat them all while they're still warm from the oven. After they cool, you can store them tightly covered in the refrigerator for up to 5 days. To serve them, reheat the cakes in the microwave on high power until the centers are soft and flowing, about 25 to 30 seconds.
Per serving (half a cake): Calories 264 • Total Fat 16 g • Saturated Fat 11 g • Cholesterol 96 mg • Sodium 42 mg