To make the crème anglaise, in a saucepan over medium heat, combine the milk and the vanilla bean, if using (if using extract, add it later), and heat until small bubbles appear along the edges of the pan. Remove from the heat and let cool slightly. Meanwhile, in a bowl, whisk together the egg yolks and sugar until thick and pale yellow, about 5 minutes. Slowly pour the hot milk into the egg mixture while stirring constantly. Then pour the contents of the bowl into the saucepan, place over low heat, and heat gently, stirring constantly, until the mixture is thick enough to coat the back of a spoon, about 5–10 minutes. Remove from the heat and remove and discard the vanilla bean, if used. Pour the sauce through a fine-mesh sieve into a bowl. Stir in the vanilla extract, if using. Let cool to room temperature, stirring occasionally to prevent a skin from forming. Alternatively, place plastic wrap directly on the surface and refrigerate until cool, for at least 30 minutes or for up to 24 hours.
Preheat the oven to 425°F. Generously butter four 3⁄4-cup molds or ramekins, dust with flour, and tap out the excess.
To make the cakes, combine the cream and chocolate in a heatproof bowl placed over (not touching) barely simmering water, and heat, stirring occasionally, until the chocolate melts and the mixture is smooth and uniform. Remove from the heat and set aside to cool slightly.
In a bowl, using a whisk or a handheld mixer on medium speed, beat together the egg yolks and sugar until thick and pale yellow, about 5 minutes. Pour in the chocolate mixture in a thin stream while whisking constantly. Gently whisk in the flour.
Divide the chocolate mixture evenly among the prepared molds. Arrange the molds on a rimmed baking sheet. Bake until the top of each cake is firm to the touch, about 10 minutes. The center of each cake will still be liquid. Transfer the cakes, still in their molds, to a wire rack and let cool for 5 minutes.
To serve, invert a dessert plate over each warm cake and, holding the plate and mold, invert them together, then lift off the mold. If the cakes stick, ease them out with the tip of a knife. Spoon some of the cooled crème anglaise in a pool alongside each cake. Using a fine-mesh sieve or a sifter, dust each cake with a little cocoa powder. Serve at once, and pass the remaining crème anglaise at the table.
Serves 4.
Adapted from Williams-Sonoma Foods of the World Series, Rome, by Maureen B. Fant (Oxmoor House, 2005).
