1/2 cup water

1-1/3 cups sugar

4 ounces unsweetened chocolate, chopped fine

8 ounces semisweet chocolate, chopped fine

1 cup (2 sticks) unsalted butter, cut into small pieces and brought to room temperature

5 extra-large eggs (or 6 large eggs), at room temperature

Whipped cream for topping

Preheat the oven to 350°F. Butter a 9-inch (or 8-inch – either works fine) round cake pan and line it with a round of parchment paper cut to fit.

In a heavy saucepan, combine the water with 1 cup of the sugar. Bring the mixture to a boil over high heat. Boil it for 4 minutes, or until a candy thermometer reads 220°F (105°C).

Take the pan off the heat and immediately add the chocolate pieces, stirring until they are melted and smooth. If the mixture stiffens, don't worry; it will loosen up again when you add the butter.

Add the butter immediately, bit by bit, stirring until all of it is used.

Place the eggs and the remaining 1/3 cup sugar in the bowl of an electric mixer. Beat on high speed for 15 minutes. If you want to prevent splattering, drape a dish towel over the mixer and bowl.

When the 15 minutes are up, turn the mixer down to low. Add the chocolate mixture, stirring only until it is fully incorporated. Do not overbeat, or air bubbles will form.

Spoon and scrape the mixture into the prepared cake pan.

Set the pan in a slightly larger baking pan and pour boiling water around it. Do not allow the sides of the pans to touch.

Place the cake in the oven and bake it for 25 minutes (note: if using the 8-inch pan you will need to cook it longer – as much as perhaps 45-50 min.). Insert the sharp point of a knife into the center of the cake; if it comes out clean, the cake is done. If it does not come out clean, continue baking for up to 10 minutes. Don't bake the cake for longer than 35 minutes.

Remove the pan from the water bath and immediately unmold it onto a cookie sheet. Remove the parchment paper. Invert a serving plate over the cake and turn it right-side-up onto the serving plate.

Serve warm, cold or at room temperature. Whipped cream is mandatory.

OChef, with changes due to Nancy McCracken