Recipe: Chocolate Rigo squares

Total time: 1 hour, plus chilling time

Servings: About 30 squares

Note: From "A Baker's Tour" by Nick Malgieri. Use high-quality chocolate such as Scharffen Berger 62% cacao semisweet chocolate.

Chocolate cake

6 ounces semisweet chocolate, finely chopped

6 large eggs, separated, at room temperature

1/2 cup sugar, divided

Pinch of salt

1/4 cup flour

1. Set a rack in the middle level of the oven and heat the oven to 350 degrees. Bring a small pan of water to a boil and turn off the heat. Combine the chocolate and one-fourth cup water in a heatproof bowl and place it over the pot of water. Stir until the chocolate is melted and smooth. Keep warm.

2. For the cake batter, put the 6 egg yolks in the bowl of an electric mixer and whisk in one-fourth cup of the sugar by hand. Place the bowl on the mixer fitted with the whisk attachment and whip the mixture on medium-high speed until the yolks and sugar are light and thickened, about 2 minutes. If you only have one mixing bowl and one whisk, scrape the yolk mixture into another bowl. Wash the whisk and bowl in soapy water, then rinse and dry them.

3. Put the 6 egg whites and salt in a clean, dry mixer bowl. Place on the mixer fitted with the whisk attachment, and whip the whites on medium speed until they are white, opaque and beginning to hold a very soft peak. Increase the speed to medium high and whip in the remaining one-fourth cup sugar in a stream. Continue whipping the whites until they hold a firm peak.

4. Stir the melted chocolate into the yolk mixture, immediately followed by one-fourth of the whipped egg whites. Sift and fold in the flour, and then fold in the remaining egg whites.

5. Scrape the batter into a 12-by-18-inch jellyroll pan, bottom and sides buttered and lined with buttered parchment or foil. Use a spatula to spread the batter evenly.

6. Bake the cake layer until it is risen (it will not rise very high) and firm when pressed with a fingertip, about 15 or 20 minutes. Use a spatula under the parchment to help lift the cake from the pan onto a wire rack to cool.

Chocolate filling

1 1/2 cups heavy whipping cream

2 tablespoons light corn syrup

2 tablespoons butter